Instructions
Turn on the PS3. Scroll to the "Settings" icon on the PS3 main menu, more appropriately referred to as the XMB. Select "Accessory Settings." Select "Manage Bluetooth Devices." Select "Yes" when prompted to register a new device.
Select "Register New Device." Put the Bluetooth headset you're using in "Pair" mode. Most headsets have a button dedicated to pairing on the headset itself. Select "Start" Scanning" on the PS3 to begin search for the Bluetooth headset.
Select the name of the headset. Enter the pass key for the Bluetooth headset using the onscreen keyboard. By default, the pass key is usually "0000." The PS3 will notify you when the pairing is complete. Press the "O" button to return to the XMB.
Scroll to the "Settings" icon again. Select "Accessory Settings." Select "Audio Device Settings." Select "Input Device."
Select the name of the Bluetooth headset. Speak into the headset and change the microphone level onscreen to adjust the outgoing microphone volume (how loud you sound to other players). The higher the number, the higher the volume. Select "OK" when you're finished.