Once your book is available for sale or pre-order on Amazon, you can start an Author Page.  You’ll find Author Central at: https://authorcentral.amazon.com/gp/home

What is Author Central used for?  Take a look at your book page on Amazon.  It looks pretty good, right.  Now take a look at the page for my book The King Who Disappeared.  Notice the header Editorial Reviews and From the Back Cover.  Where did they come from?  That isn’t stuff you can add when you uploaded the book to Kindle, but it is content you can add on your Author Central page.

Your Author Central page is a vital marketing tool. Don’t neglect it. You can set up an Author Central page using this link: https://author.amazon.com/help/G2SNTAVHXHD4S6S3

Fill in as many categories as you can for your book and subsequent books. Author Central will create a separate page for each book you publish.