using inputs on the front of cable box??

so i have been trying to figure out how to use the front inputs on my comcast motorolla cable box. they say audio and video in so i know they are inputs. but i can not find where to change the input source. this is really stumping me becasue i know this should be really easy and im not completely dumb when it comes to this stuff, but i can not figure this one out. please help!

 

have you tried reading the manual? I'm sure its in the menu somewhere.

 

i have i looked it up online and it didnt say anything about the front ones. ive never had so much trouble with something this simple lol

 

whats the make/model of your cable box

 

im actually out of town and wont be able to look at it until wednesday but all i know is its a motoralla hdtv version if that helps