cd changer install help needed!!!

can someone PLEASE help me. SO i got my car this weekend and let me say first, I am obsessed. I keep pinching myself to check if this is a dream or not. There are no words that can describe the drive of the car, the handeling, the feeling you get just sitting in it, the feeling you get looking at it when walking away after parking it.. sigh.

anyways...i need some help please. I tried to install the cd changer. everything went smooth until it was time to plug it into the wires in the trunk. I only found two different plugs and they fit into the back of the changer. However, there is one small round plug still there. my cd changer won't power up or be recognized by the nav system. are there 3 wires that go into the changer? if so, where is the 3rd wire? i took the little plug out of the navigation system and plugged it into the 3rd slot on the cd changer. it fit but still didn't power up. so im guessing a similar plug should be there for the changer. i only found two wires in the bundle behind the mounting bracket. PLEASE HELP! im guessing one is for the power. one is the audio out..and the other a possible negative for the power?!!? but i cant find it. and i dont want to go back to the dealer looking like a [email protected]$$ and paying a 100$$ for installation!!!!

THANKS in advance!!!