The Ing side of the switch feeds the coil + side and the brake lite switch. The Acc side feeds the headlight and tail light. No wires return, they only go to the thing you want to power. If you have a headlight with a three prong plug one of the side prongs is the ground. Take your light and two jumper wires and a battery. connect one wire from ground - to a side prong, connect the other wire to the positive + side of the battery and touch it to the two remaining prongs. Watch how bright the bulb lights up. Then put the ground on the other side prong and touch the remaining two again. One way will light up the bulb really good (hi & low) Now you found your ground for the light, hook it to a good ground and the other two prongs are your hi & low sides. Two prongs = one ground and one light. use the same method. One wire (most Cubies and most rectangular lites) = the wire hot and the case the ground. Use the Magneto, 12v two brush, bosch reg, and battery diagram. It shows a mag so ignore that part. Run a wire from the Ing side of the switch to the + side of your coil and a wire from the - side of the coil to the points.