I built a SaaS that nobody asked for, now what?

Hey, I built yet another VoIP SaaS business, registered it, and even handled the paperwork. In my head, it was a great product; in reality, I have no clue how to sell it or where.

Every day I say, maybe I need to add a feature or make the mobile app, but I know this is not the right thing to do; I need to find people who want it. It's just, I have no clue where...

For solo founders and software makers who are profitable, how did you sell it at the beginning?