You can make your new books available for pre-order in Kindle Stores worldwide. Setting a pre-order allows customers to order your book as early as 90 days before your book’s release date. When you make your book available for pre-order, customers can order the book anytime leading up to the release date you set and it will be delivered to them on that date.
One advantage of pre-order is that you can start promoting your book before launch to help raise awareness. You can promote your book’s pre-order page on Author Central, Goodreads, your own site, and elsewhere. Also, pre-orders will contribute toward sales rank and other Kindle Store merchandising even before your book is released, which can help more readers discover your book.
You’ll list your book as you would with any other KDP book. When you’re adding a new book, on Step 4, “Select Your Book Release Option,” you will choose “Make my book available for pre-order” and set a date in the future. That’s it.
via Amazon Kindle Direct Publishing: Get help with self-publishing your book to Amazon’s Kindle Store.