I really do not have much experience with this subject since I have not published an actual book yet. I do have an episode story but I wouldn’t necessarily call that self-published because it is through a writing company that is allowing you to use their services as users. Though I would check these links to help you out if you are a self-published author. I know it can be harder to be self-published versus working with an actual publishing company but it’s not impossible. It takes time to get to a popular point when promoting your published work. I know social media is a huge part of the process when it comes to getting exposure. I know that @ShanniiWrites has self-published a book on Amazon so she might have some more advice as well. Check the links out!
https://medium.com/swlh/how-to-market-your-self-published-book-with-a-limited-budget-b18ef288e3ff