Not all E46s came with Bluetooth - what I've heard is that the coupes all have the buttons on the steering wheel for it but that doesn't mean it was ever enabled or functioning. My 2005 325Ci had the buttons but no Bluetooth.
With that being said, the easiest way to find out is to press the R/T button on top of the one with an icon of a head that's speaking. If you are Bluetooth-enabled, the radio should read "searching." That's when you would use your phone to search for the connection, enter the PIN, and you will be linked from then on whenever the car is on.