Remove the cable from the (front radio) it should plug into the (rear tuner) .
Plug this cable into the extension and then into the jack labled "front gerat" on the CD
take the black connector and plug it into the "tuner" jack on the CD.
Plug the other end into the jack that the first cable to the tuner was removed.
Remove the power cable, plug in the extension, one end goes into the CD the other in to the 'tuner'
I think the CD sits upright in the wheel well opening, the arrow on top should point to the front of the vehicle