Plug the wiring harness end (with the eight-pin Weather Pack-type connector) into the back of the computer/display unit. A click will indicate the connector is locked in place. The heavy red lead coming off the harness is for a 12-volt source to power the dyno. Connect it to a power source that turns on and off with the ignition key. The heavy white lead connects to an instrument light source and the heavy black lead connects to a chassis ground.