Create an account with the U.S. ISBN Agency at Bowker through their Myidentifiers.com site.
Determine the number of ISBNs you wish to purchase. It's recommended that you purchase enough ISBNs to meet your publishing needs for the next five years. The more ISBNs you purchase, the less each of them cost. As of January 2011, ISBNs were $185 each, $250 for 10 or $1,000 for 1,000.
Click on the box labeled "ISBN" near the top of the Myidentifiers.com site. Select the "Buy ISBN" option.
Complete the purchase of the ISBN(s). The number will be e-mailed to you.
Assign the ISBN to the book you've completed.
Register the book's title as it corresponds to the ISBN number at Bowkerlink.com. This will ensure your publication is listed in resources such as "Books in Print."