This article explains how to connect your Xbox 360 to a wireless home network if you have a wireless router installed in your home. Instructions apply to all versions of the Xbox 360.
How to Connect Your Xbox 360 Console to Wi-Fi
You can access a wireless network through the system settings on your Xbox 360. Here you will find the relevant settings.
Connect the appropriate wireless network adapter to the console. (The Xbox 360 can also be connected directly to your router with an Ethernet cable.)
Turn on your Xbox 360 and select the Settings panel from the home page.