Starting in the back of the car, connect the bluetooth module. The module will connect directly to the wiring in the car depending on the telephone configuration of your model year and telephone wiring

Newer BMW E39s, starting with March 2002 Production cars will have the 54 pin telephone wiring plug that connects directly to the Bluetooth module

Older BMWs will have different wiring connectors if prewired for telephone, or a telephone wiring connector if not prewired for telephone