By a rod that goes up the steering column. There is a selector on the center of the steering wheel. The positions/functions of the selector are shown on the wiring diagram (the lighting switch diagram is a 35 but similar to a 36). Your wire harness to the bottom of the steering box should look something like the one posted, except old, covered in grease, faded and brittle LOL. There are four positions on the lighting selector switch: OFF, PARK, LOW BEAMS, HIGH BEAMS. Per the wiring diagram, you also get power to the STOP LIGHT switch and to the INSTRUMENT LIGHT switch and power to the TAIL LIGHT(S) in any position other than OFF.