Purchase an International Standard Book Number (ISBN) for your book. Every book sold in bookstores and many self-published works have an ISBN, and Apple requires your book to have one in order to be sold in the iBookstore. You can purchase your ISBN online; the price of a single ISBN is $125 as of January 2011, and it takes approximately 15 business days for your order to be processed.
Convert your book file into the ePub format, which is required for the iBookstore. There are many programs that allow you to convert other file types into ePub, including Calibre and Adobe InDesign. It is also possible to do the conversion without the help of a program by turning your manuscript into a series of XML and XHTML files and grouping them into a zip file.
Obtain a U.S. tax identification number from the IRS, if you don't already have one. Apple requires everyone who sells their work through the iBookstore to have an Employer Identification Number (EIN) even if they do not live in the United States. Despite its name, you do not need to have employees in order to get an EIN, and you can apply for one online through the IRS website.
Sign up for an iTunes Store account. You will need to create an Apple ID and password and then provide your credit card information to be kept on file with Apple.
Apply to sell your book in the iBookstore via Apple's iTunes Connect partnership program. You will need to provide your personal information and upload the ePub file of your book for review. You should be notified via e-mail within 24 hours whether your submission has been accepted or not.