in the back of the radio is a big connector that has three individual connectors built in. one of those 3 connectors is black and has 12 pins...

assuming that you have factory harness 65 12 0 153 502 with a 12-pin black plug hanging with 3 wires in it, you will pull the wires with pins from the harness and snap them into existing 12-pin black plug - brown/white (ground) into slot 10, yellow/white (left channel) into slot 3 and blue/white (right channel) into slot 1. if, somehow, your factory radio is missing the black plug altogether, and you have just a blue and white plugs, then you just snap in the black plug that came with the harness, into available slot inside the big connector, that's it...