how to hook up an alternator for a 85 caddy?

Do a Google search for "GM alternator wiring diagram". But basically there is one big wire and two small ones The big wire goes to the positive battery cable. One of the small wires connects back to the big terminal, and the other one goes to the "On" terminal of the ignition switch.
If you can't find the two small wires, you can buy a "one-wire" GM alternator. Those hook to the positive battery cable only.