I have a red wire and a black wire not sure sure which wire goes where on furnace for the central air

Without knowing what type of furnace you have, a little more info would help. Again, not knowing anything, a red and a black wire usually infer 240Volts. Are there terminals? how did these wires just appear? Did you take them off? Are they from a piece of wire? Are they solid or braided? Can you read any markings?