I don't have the NAV system but at a guess......
You plug your Ipod in and wait for the VW Sign to come up on the Ipod screen that tells you that it's connected. If you don't have the MF steering wheel your controls will be like a normal cd player with the arrows for backwards and forwards.
I hope I'm right in telling you that if not I'm sure someone will be along soon to help
Steph xx