Easy. Assuming you have product to market fit, all you need to do is figure out where the people for whom your product solves a problem are 'hanging out'.
You then need to come up with a simple plan to get them used to the idea that you or your product can solve their problem and then introduce them to the product.

None of this costs any money. In fact, even with companies that *have* money, I encourage them to use these routes over things like advertising because it's far more potent.

Hope that helps you understand better, and gives you some clarity (no pun intended).
If you need any further advice, feel free to call me. I should be able to help clarify everything in less than 30mins.