1998 bmw 540 antenna connection

You can connect behind the head unit or on most of the vehicle in the model year the wire from the internal rear glass antenna follows the right side (as you are sitting in the car). The connecter from that to the extension to the head unit is along that line and again in most can be found behind the seat or under. If its not there check the other side as some of the glass has been changed and I havebeen told by a glass installer that most of the newer ones are on the left.