Kindle Direct Publishing (KDP) is the Amazon publishing platform. Their primary focus is to get your print and eBooks onto Amazon, but they also allow you to distribute through Ingram, but it is best for an author to distribute through Ingram directly because the royalties are better. But do not ignore KDP, they have overall the best royalties for listing books on Amazon, and most authors will sell more books on Amazon than most other sources.

KDP is simple to use, and the company publishes video tutorials to help you learn more about the formatting and process needed to list books.

They will assign an ISBN, but you only want to use this option if you are not planning to list on other distribution platforms because the ISBN they assign you cannot be used on other distributors.