Eclipse 2001 gs Infinity Head Unit

EDIT:

After playing around with my head unit, i found that there's an open slot (for something to plug into) on the back of the infinity head unit. After research i found that it is a 13 pin din plug.

I purchased a 13 din pin plug/3.5mm adapter and hooked it into the infinity unit...it seems to do nothing to the unit at all...

Anyone know if im doing something wrong? There isnt an Aux option on the infinity head unit...do i just burn a blank cd and play it with an mp3 player?

Thank you in advance.