There is a bolt on your intake manifold, near the base of the distributor. Loosen the bolt, then rotate your distributor. If you're adding advance, you will hear your idle pick up. The best way to set timing is to set your idle where you want it, hook up a vacuum gauge, adjust distributor until you get maximum vacuum, reset idle, tighten distributor, etc... Or, since you just bought yourself a timing light, 12 degrees is a good start, or just advance it until you hear knocking or preignition. Then back off a few degrees. Reset your idle, and drive up a big hill in a high gear to make sure you don't preignite. If you do, retard the timing a bit.