Hello!
My car has a head unit with a cd player but no aux input, so i found a bunch of videos on youtube on how to install one, via a jack cable, but i have a problem: the pins on my head unit's motherboard are not labeled so i don't know which one is right/left channel and ground.
The connector from the cd reader to the mother is a 14 pins ribbon.

 

When your car doesn't have Aux you simply purchase a "FM Transmitter" that your aux device plugs into and you set your radio to the proper FM channel and it plays the aux.