When you open any of the doors look down. You will see the plastic covering where the carpet stops ( carpet covering ). you will notice another vertical plastic covering on the B pillar where the first carpet covering joins on to. route the wire under the front carpet plastic covering, the B pillar and the rear carpet covering. It all is held down by clips, pulls out very easily.
Pull the back seat out (just pull the front upwards - only 3 clips that hold it down) and route the wiring under the seat to the trunk. put the seat and plastic coverings back on and you shouldn't be able to see wire anywhere.
PM me if you need more info