KENWOOD 5120 xm sirus????

Ok I drive alot for work so just bought a portable satelltie radio for my work van but wanna be able to switch it back and forth to my truck. I see the xm and the sirius option in the kenwood but how do I use that? also i have an aux port right on the front of the headunit and i cant seem to get it to work using the aux? how do u use the aux on the headunit?
Thanks guys

 

also I have an xm radio for my van if i got the tuner for my kenwood even tho its sirius it should work cuz there the same now right? will it cost me ne more monthly?

 

see thats where im confused cause i have an xm but on kenwoods site the docking station and all the wiring and stuff to play through my kenwood is sirius. do they make one for xm?
Thanks