You need an interface. Build your own from circuit on the board or buy a Resler interface (resler.de). Hook laptop to interface, hook interface to car at a point where you can get 12 volts, ground, and I-bus. Get the SW for navcoder from kiwijochen and go. I have a 3 pin plug connected in the trunk of my e38 for hookup. There are points near the left trunk area where you can find the 3 wires.