If you have more than one IR-equipped computer at the same location, you’ll probably want to "pair" each computer with a specific Apple Remote. Pairing sets the computer to take commands only from the specified remote. You can pair your computer with only one remote at a time.
1. Hold the remote close to the computer (3 to 4 inches away) and point the remote at the front of the computer.
2. Press and hold both the Menu and Next buttons on the remote until the paired-remote graphic appears on your screen (about 5 seconds).
To remove the pairing, open System Preferences, click Security, and click the Unpair button. Your computer will now take commands from any remote.