If you're not using Mac OS X 10.6.5 or later, update your software before continuing. Then make sure that Bluetooth is turned on and the trackpad is in discovery mode. Finally, pair the trackpad with your device.
Make sure that Bluetooth is turned on
Choose Turn Bluetooth On from the Bluetooth status menu 
in the menu bar. Or choose System Preferences from the Apple menu, click Bluetooth, then click Turn Bluetooth On.
Put the trackpad in discovery mode
While the trackpad is in Bluetooth range (about 33 feet) of your Mac, press the on/off button on the trackpad. Then check the indicator light in the upper-right corner:
- Light glows steadily for 3 seconds, then flashes: The trackpad is in discovery mode, ready to be paired. It remains in discovery mode for about 3 minutes, then turns off.
- Light glows steadily for 5 seconds, then turns off: The trackpad is already connected to a device in Bluetooth range. The trackpad remembers several of the devices it most recently paired with, but connects with only one of them at a time. Either unpair the trackpad from the other device or move it out of Bluetooth range of that device.
- No light: You may need to replace the trackpad batteries.
Use a wired USB keyboard and mouse during setup
During the setup process, use a USB mouse to speed up the setup of your Apple Magic Trackpad. Keep a USB mouse connected to the computer until you've completed setting up the trackpad. After setup is complete, you can disconnect the USB mouse.
Follow the setup steps below to make your Apple Magic Trackpad discoverable and pair it with your Mac.
Set up your Magic Trackpad
- Open Trackpad preferences by choosing System Preferences from the Apple () menu then choosing Trackpad from the View menu.
- Click Setup Bluetooth Trackpad in the lower-right corner of the Trackpad preferences pane.
- Turn on the Magic Trackpad by pressing the on/off button until the indicator light comes on. The indicator light glows steadily for 2 to 3 seconds to indicate the batteries are good. After that, the light will blink to indicate your trackpad is in discovery mode.
If the light on the trackpad does not glow or flash when you turn on the trackpad, make sure the batteries are properly charged and installed. - After five to ten seconds, the Magic Trackpad name should appear in the Search preferences.
- Click Continue. The Setup Assistant will try to pair with the trackpad.
- When the computer and trackpad have successfully paired, the Trackpad preferences pane will expand to show all configurable options and battery level in the lower-left corner.
You should now be able to use your Apple Magic Trackpad.
Set up your trackpad if you don't have a USB device
If you don't have a USB device, Mac OS X may be able to pair your wireless device without it.
