Conventual Amazon wisdom is that Amazon won't promote your book until you've made some sales.
Promote means to show it in results for various searches so that people can find it and potentially buy it.
Now that's a Catch-22 of course. You have to make sales for Amazon to promote it, but how can you make sales if they don't promote it?
And the answer is advertising.
Amazon allow you to run an advertisement targeting nominated search terms, your book may appear for a given search term and you'll pay a fee when someone clicks on your ad (whether they buy the book or not).
When I created an ad and tried to run it, I got a message saying that Amazon doesn't allow advertising for erotic works.
So here are some posts I've made to this site, with the aim of getting visitors to enjoy my work and buy some books. It worked for 50 Shades of Grey: