Instructions
Power up your 360 console to check the ON light on the adapter; if the indicator isn't lit, press on the adapter's USB connection to ensure the plug is in correctly, or completely disconnect the USB cord and re-plug it in.
Position your console closer to your wireless router should the above not correct the problem. Make sure there are no obstructions between your console and your router and check the router to make sure it's powered up.
Power down any other electronic devices that may interfere with your router's signal, like some cordless phones, cell phones and some microwaves. Check the security settings on the network you're using by ensuring the settings on your adapter match those of the wireless access point, such as your WEP key matching your WPA pass phrase.