Alright, so I got a 2001 A6 4.2L blah blah and so on the truck it has a antenna that says Navigation GPS. It has the controls by the e-brake like "Nav" "Return" and the ***... But how do I start it?

I looked in my booklets and it says by pushing Nav it should start, but it doesn't. Its like those controls don't do anything. I have the Symphony deck, I was wondering If I needed the RSE-N Navigation Screen but I really really doubt it.

Is there anyother steps or anything else I should know or am doing wrong? Thanks