Method 1
Look on the bottom of the AirPort Extreme. If you are connecting using wireless, you need the AirPort ID. If you are connecting using a wired connection, you need the Ethernet ID.
Method 2
Open Macintosh HD > Applications > Utilities > AirPort Utility
Click on the AirPort Extreme, then click Manual Setup
Look for the AirPort ID and Ethernet ID on the Summary page
