I pulled my xm GEX-P900XM system out of my wrecked car and tried to install it in the new car. When I went to install it in the new car I realized the grounding cable was disconnected from the GEX-P900XM. I bought some grounding wire I just don't know where to connect it into the power harness. Do I hook it up into the slot on the opposite side of the power cable or what?...

It is the far side of the power wire(not the middle one). Good luck.