Cohiba, basically all you have to do is to write a book, format it correctly, set up an Amazon account and upload it to Amazon, set your price and then you just kick back and start wondering when the money is going to come rolling in. Your percentage will depend on the price that you sell your book for. It is also a great big help if you have some way to promote your book, if you have a popular blog where you can talk about it or something like that. I don't, and so far it has sold enough copies that I can almost afford to go to red lobster and eat dinner. The average e-book sells 450 copies, so don't get your hopes up too high. This link will tell you all that you need to know.
https://kdp.amazon.com/self-publishing/help?topicId=A37Z49E2DDQPP3
https://kdp.amazon.com/self-publishing/help?topicId=A37Z49E2DDQPP3