Instructions
Wired Network
Turn on the Xbox 360.
Plug one end of the network cable that came with the Xbox 360 into the Xbox and the other end into the router.
Turn on the Xbox 360 and create a user profile.
Wireless Network
Turn off the Xbox 360 and unplug the network cable running into the Xbox 360 if one is currently installed.
Plug the wireless adapter into the I/O port on the back of the Xbox 360. Turn the antenna on the wireless adapter facing outward.
Turn on the Xbox 360.
Click "System > Network Settings." Click "Edit Settings > Basic Settings." Select your wireless gamer router.
Enter your WEP code for the router, then select "Apply Settings." Click "Test Xbox Live" and your Xbox 360 should connect to the Internet.