Read up on sales, figuring this out is part of the sales process. The answer is different for every company, though there are patterns. For small companies, it's usually closer to the user than you are thinking.

To Sell is Human, The Challenger Sale, Crossing the Chasm, The Little Red Book of Sales

Don't do ads until you have a repeatable sales playbook and never outsource lead gen

You will learn sooooo much by studying and doing founder led sales. It will pay itself back many times over