1. Go to the Apple Menu > System Preferences > Network
  2. Click the “+” symbol on the bottom left
  3. Under “Interface” choose “Bluetooth PAN“. Under “Service Name” put what ever you want. Click Create. Close the Network screen.
  4. Ensure Bluetooth tethering is On within your iPhone 3G/3GS and that Bluetooth is On within your Mac.
  5. Navigate to the Bluetooth menu item on the Apple Menu Bar and highlight your iPhone 3G/3GS and click “Connect to Network”.