Instructions
Connect each of your two Xbox 360 consoles to a separate television set using the included audio/video cables.
Make sure that both consoles are powered off before starting the connection process.
Plug an Ethernet cable into the back of the first Xbox 360.
Connect the other side of the Ethernet cable to the back of the second Xbox 360.
Turn on both television sets and both Xbox 360s. Because the Ethernet port is in use, each console will automatically display the system link screen on each TV. Press the "A" button on both controllers to confirm and establish the system link.