Instructions
Connect to the Internet using a broadband service. You can attach an Ethernet cable to the back of the console to establish a wired connection or buy a networking adapter to connect wirelessly.
Go to "My Xbox" at the Xbox 360 Dashboard and choose "Sign-In." Follow the on-screen instructions to create your profile if you are a new subscriber.
Select your profile and go to "Account Management." Choose "Manage Account" and then "Redeem Code."
Scratch off the back of the subscriber card to reveal the PIN. Enter this number to activate your Xbox Live account.