Instructions
Turn on your Xbox 360.
Choose the "My Xbox" listing from the main Xbox 360 menu. The main Xbox 360 menu is referred to in official documentation as the "Dashboard." From the menu that is being displayed on your TV, select "System Settings" followed by "Network Settings."
Select the name of your AT&T U-Verse network connection.
Use your wireless Xbox 360 controller to enter the password for your AT&T U-Verse connection (if applicable). Once the password is entered (or if no password is present), your Xbox 360 will be able to use the AT&T U-Verse connection to get online.