How do you use timing light?

On most cars, there is a timing mark on the crankshaft pulley. It will be just a notch on the lip of the pulley closest to the timing cover. On the face of the cover there will be either a pointer sticking out or a series of lines with numbers above each line. 0, 5, 10 or 0, 10, 20. 0 is top dead center on number one piston. Attach the battery clips to the battery and the pick up on the number one spark plug wire. Start the car and the light should flash each time number one cylinder fires. There should be a sticker on the radiator support or hood that says what the timing should be, probably somewhere between 4 and 8 degrees BTDC. Before top dead center. Shine the light at the crankshaft and because of the strobe effect, you will be able to see the timing mark on the crankshaft and adjust as needed. You adjust the timing by loosening the distributor and rotating is slightly one way or the other. If there is a vacuum advance on the distributor, disconnect the hose and plug it when you set the timing. Some cars have the timing marks on the transmission flywheel or torque converter and there is an access plate on the top of the transmission housing.