How-To: Facebook fan page username
Facebook allows you to have a username for your fan page. To select a username, a user with admin privileges can go to www.facebook.com/username. Underneath the box containing profile options click on “Set a username for your Pages.” Use the dropdown to select the correct page. Enter in your desired username and click on check availability. If it’s available, click confirm.
Once you have claimed a username by clicking the “Confirm” button, it is not possible to edit it, or to transfer your username to a different account on Facebook. Additionally, when an account is removed from the site, its username will not be made available to other users for security reasons.
All Pages are eligible to claim usernames if they have more than 25 fans.