I have lots of pages in this area on what to do, but to summarize, you need to:
Selling with Amazon Advantage
Once you have two or three physical copies of the book in your hand, sign up for Amazon Advantage. It's their way of allowing normal people to sell items in their marketplace. It's very cheap and now you can have your book listed in Amazon's gigantic library. This can be a critical way for people to find you and to enjoy your works.
I know Lulu has the option to let you automatically list your book on Amazon, but that then greatly inflates the price of the book in ALL systems because of the way pricing works. Amazon wants to make their profits and if they are listing a book for $14.99 including their cut, they don't want other sites able to list it for $9.99. So it's better to let Lulu list it inexpensively and then manually list it in Amazon and other sites if you wish.
Don't forget to customize your Lulu "thank you note" so that anybody who does buy one of your books gets a personalized note from you. This can help you build up a conversation with your loyal visitors.
Also, be sure to customize your Lulu author profile page. This can help build a connection between you and your readers.
After that, the next step once this is ready is to start mailing copies of your book out to reviewers, and to get your family and friends to read and review your book on their websites, blogs and in Amazon. The more reviews you can get out there about your book, the better your chances are that people will buy it!
I've got thousands of pages on marketing and promotion. Once your book is live, it's time to get started on that aspect of selling a book!
Publishing On Demand Step By Step - Lulu
Lulu Self Publishing - Setting Up the Book
Formatting your Book for Self Publishing
Creating a Lulu Covers
Setting the Lulu Description
Setting the Lulu Preview
Promoting your Lulu Book
Problems and Issues with Lulu
Ebooks on Lulu
Lulu Self Publishing Main Page
Lisa Shea Free Ebooks
Lisa Shea Full Library of Published Books
Getting Your Book Published
Writing Tips and Online Books
Lisa Shea Medieval Romance Novels
Online Literary Magazines
Lisa Shea's Homepage