The cab lights come with a wire harness. all you have to do is attach the two wires to the right spot and your done. its VERY EASY just remove the plastic/metal shroud to get to the back of the light switch knob. If you are installing oem ford cab lights splice the brown wire coming from the cab lights to the brown wire coming from the back of the light knob (thing you turn to get the lights to turn on). other wise its the brown wire you are spicing to. BROWN=parking and running lights. when you splice the cab light wire into the brown wire coming out the back of the light knob your cab lights come on when you have your parking lights on, your running lights, and if you have keyless entry when you lock your car they flash. ALSO THE GROUND WIRE: it can go any where. ANYTHING THATS METAL. just cut the tip of the wire to expose the copper wire and put under the head of an existing screw and tighten it down.