Sorry, but this question is a bit backwards. You need to have an audience/need for your product or service BEFORE you create it.

Having said that, I'd go back to the basics:

a) create a niche
b) determine an ideal client profile
c) design a business plan

The lack of specifics to your question make it impossible to help you so I can only answer with the same vague generalities in which the question was asked. Basic signs of product market fit:

High CTR on ad spend: if you're seeing above .3 Unique CTR on your ads, that's a good sign that people are interested in what you're offering.

High conversions on landing page or install:
On a web page, a general first funnel conversion of something with traction will be 20% or above. For a mobile app, it will be account activation of 35% or more.

Next comes user love. User love is expressed many ways. Engagement is most obvious but in early days, non-incentivized social shares are a promising sign. So too are customer feedback messages with praise and thanks.

Happy to talk to you in a call about what you're doing.

To know the right product market fit you need to talk to your target customers. That's the best way.

Ask them things like:

what are your biggest challenges when it comes to <your niche>?
why is this so big problem?
what is going to happen if you don't deal with this?
how do you think you can deal with this?

When you find out what are their biggest challenges and pain points, create a product that helps them to solve them.

Ask them again for an interview and present them the solution. Look if they'd buy it. Search for objections why they won't use it. See if you can eliminate them in some way. Pivot your offer according to that.

Talk with at least 20 prospects per week and present them what you're doing and what's your progress. Ask for feedback all the time. Then, and only then you're going to build a great product.

By looking for feedback you eliminate guessing. And that's really important for success.

Feel free to schedule a call if you want more help with the product launch. I'd love to share my experience with you when it comes to identifying and connectin with your niche, how to validate your idea, get to product marketing fit and launch your thing successfully.

Wish you all the best,
Martin

Everybody keeps making the same mistake. Find a hungry crowd and it doesn't matter if you are selling hamburgers or steak, they will eat.
Always find your market and adjust your product to meet the demand.
Don't stop taking massive action.
Best of Luck,
Michael T. Irvin
michaelirvin.net
My books are available exclusively through Amazon Books. Check out my book "Copywriting Blackbook of Secrets"
Copywriting, Startups, Internet Entrepreneur, Online Marketing, Making Money

Perhaps ask the question differently. Find the market needs, then ensure that your product meets those. Why? Because being a product in search of a problem is no fun at all.

This article is based off of a question posted on Quora:
"What's the best way for a first-time entrepreneur to determine product market fit?"
Based on the way the author framed it (using "first-time entrepreneur"), I assumed he was or is under a tight budget. If this is the case, he will have certain limitations in testing and determining PMF - namely, he cannot simply task this off to an agency (not would I suggest that be the only way he or any startup test PMF before launch). I would suggest the following regardless, but it is especially necessary under tight budgets OR if an investment team needs these questions answered before deciding to fund a project.
First, I agree (in principal) with The Lean Product Process:
1. Determine your target customer
2. Identify underserved customer needs
3. Define your value proposition
4. Specify your Minimum Viable Product (MVP) feature set
5. Create your MVP prototype
6. Test your MVP with customers
Where I can add value is by walking you through one approach I have used for steps 5 and 6 in more detail below...
Aside from what you would discover in articles online through a simple google search (I took the liberty of summarizing some good one’s below), my approach to determining PMF very early on, and very inexpensively, has been to:
1. Find/buy an affinity domain name phrase that exemplifies your value prop (i.e. "EasyInsuranceRate.com" for insurance quotes). The reason you test PMF through a vanity URL first is because you want to know if the value proposition can stand alone and sell without a bunch of PR and fluff around it. You want to target your specific market, in the easiest way possible. Find a phrase that relates to your market will bring more users to your platform than a more unrelated name. This will be your landing page in a sense. This is the attention-grabber, and it needs to be simple.
2. Build out the microsite (simple Wordpress install or a landing page builder tool will do) under this domain with the same copy/creative they plan to use on your branded site. This technique is being used by large companies like Snapchat and Spotify. The idea here is to actively engage the user in clicking onto a that microsite in order to narrow down the focus of your product.
3. Create a the hook (an offer to get involved in a beta test, be shipped a sample, sent a coupon code...). Before selling an audience, you need a way to understand if they want what you're selling. Email capture is a good start. Create a good hook that is relevant to the final product and highlight that offer on your microsite's home page.
4. Launch traffic to this funnel from a variety of target persona's/interest/demo's. Invite potential prospects in by using descriptive words that would produce interest in your product. Watch the wording of these CTAs.
5. Use ads in ^ campaigns to test out the copy and call to action you are considering. Ads are placed everywhere on virtually every website today. Use this to your advantage and make buyers feel almost obligated to click/browse your page by posting intriguing ads on your page.
This process allows you to see real numbers and costs to market your product/service to those audiences. If they will buy from a vanity URL, or even leave their information to receive early access, you can feel confident a percentage of those will sign up or buy your product at least once.
Review all results and data. If all is going well - engagement is high, CTR is over 3% on ads, you are capturing emails from over 5% of traffic... You can be confident you have PMF.
As you progress through your PMF determination phase, the questions you need to get answered to get to a product market fit answer:
1. Who are your first 20 customers and what did it cost/take to acquire them?
2. Will online audiences buy your product or sign up for your service after clicking an ad?
3. What were your unit economics for the above ad channels^
4. What changes when you add credibility to you sales funnel (influencer mentions, testimonials, client logos…)?

One-on-one interviews with your users and customers help you identify problems, generate ideas, improve your product, and build relationships. It also forms the basis for your initial thinking around customer segmentation. Mike Fishbein’s ultimate list of customer development questions is a particularly good resource if you need to start building a list of customised questions. Another way to collect data is through your internal team members, especially customer staff. The context for customer feedback is always crucial. A piece of feedback that does not look relevant today might be good six months down the line if you switch focus to different markets or business goals. For example, if your next quarterly goal is to reduce churn, you can then specifically look for feedback submitted by churned users. If you are an early-stage start-up in need of cash, you might be tempted to say “yes” and build new features to get more paying customers, but that is not necessarily a good idea. To build a sustainable company, short-term revenue is not the business metric you should be targeting and measuring yourself against. Do not launch into developing a feature just because somebody asked you to. Do not blindly accept customers who are a bad fit.
You can read more here: https://www.hotjar.com/grow-your-saas-startup/product-market-fit/
Besides if you do have any questions give me a call: https://clarity.fm/joy-brotonath