How to select the Aux input
 

How in the heck do you select the Aux input?? I just purchased a used '08 C300, and the aux jack in the glove box is already set up for an iPod with cord and all. When I plug the iPod in, the iPod screen shows a Mercedes logo and says "connected." But, I can't find any way to play the music or get the system to recognize it.

To select the audio Aux mode, the manual says: "DISC --> CD/MP3 --> Aux"

But when I press the DISC button, it starts playing music that the previous owner had on his hard drive (a CD of Jeezy). When I slide the audio controller knob, it selects a new track, but there's no way to select anything that says "CD/MP3". Those words aren't even on the screen. Instead I see the following:

At the top: Navi, Audio, Phone, Video, System
At the bottom: Music Register, Folder, Changer, Sound

To my knowledge, there is no way to select the options at the bottom.

Pressing "Back" does nothing. Pressing "CLR" also does nothing. If I push the knob down I can navigate the folders of the hard drive, but there's no way to do anything useful.

Can anyone tell me what I'm supposed to do? It seems like this should be really, really easy.

Bump. Anyone? How to select the iPod?

Are you pushing and holding the CD/MP3 button? This should show the Aux mode.