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.
Thank you for your answers; I've learned a lot. I should summarize the purpose of my product and the development process, clearly outline the pain points it addresses, and promote it on various platforms. However, I'm a bit worried because those larger platforms may not be very friendly to new users, and it feels like the content I post might not get much visibility.
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.