The Aux input cable connects too the wiring plug behind the navigation display. In cars without navigation, the process is the same, but you will remove the radio headunit instead of the navigation display

With the navigation display removed, locate the 3 pin Aux Audio plug on the harness

Simply plug in your 3 pin male plug on the Auxillary Audio input cable into the 3 pin female plug in the car

Once connected run the Auxillary Audio input wiring to your desired location.