handiest way to do it is to run a length of two core cable down the car to under the rear seat and tap into the earth wire of the fuel pump .to do this you need to cut the earth wire and join in one of the wires from the two core cable in to one side of the cut and then the other wire to the other side of the cut ,then insulate the joins with tape or heat shrink ,the other end of the two core wires need to be joined into a switch and placed out of view under the seat or some where like that , hope this helps