Instructions
Update the PS3's system software. Version 1.3 or higher is required to use the remote with your PS3. The "System Update" option is located at the top of the "Settings" column of the XMB.
Open "Accessory Settings" from the "Settings" menu and select "Register BD Remote Control." Hold the "Start" and "Enter" buttons on the remote until the PS3 finds the remote. Follow the onscreen instructions to finish pairing the remote.
Turn off other Bluetooth devices near the remote or PS3 and try registering the remote again.
Replace the remote's batteries if the PS3 still doesn't see the remote.