Start telling your story about why you built it in the first place. Tell it on any community that you think people who are in a similar need will be. Get narrow, try a few small niches. Stick with it for a month and then see who is following along. That is your audience. Start to tease out features based on outcomes that those people will achieve once they are helped by your product. Let your audience tell you what they want.

Paid ads, etc, will very likely not yield good results at this early stage because you don’t know your ideal customer profile well enough and no one knows you or your product well enough to trust you. This will build over time.