Be careful here, with a convertible the TCU is not in the "normal" coupe or sedan location. It is in the trunk, but a PITA to access.
Not all cars had the BT option, also ALL the documentation regarding the BT pairing is mostly incorrect, or at least any reference to a pairing button.
If your car has SOS, then likely you have the BT, but no guarantee. Additionally you could have either the TCU or ULF module and it could be disabled electronically. Also the BT systems are known to hang and many times you have to pull a few fuses to "reset" the BT module so it works again.
First thing you should do is hold down the microphone button on the steering wheel for about 10-15 seconds and see if you get a woman's voice for voice command. If you do, then you have a BT module in the car. If you do not get a woman's voice, then you may or may not have a BT Module.
The later model cars go into pairing mode automatically when the car is started like the previous poster noted. You should be able hit your T/R button on the steering wheel and see if the radio says "Searching" when the car is started.
You will need either NavCoder or BMW Scanner 1.4.0 if the module is disabled. Do not waste your time or money with a dealer, they are too expensive and know far too little about the BT modules in these cars.
If you do not have a BT module, you can likely add one, but it expensive and there may be other options to check out.