How do you remove rotor on 1988 cutlass supreme?

You need to remove the caliper. Usually there are 2 bolts/pins that go through the calipers, holding them in place. Once the calipers are off, the rotors should come off quite easily. If it's a front wheel vehicle, the rotor should just pull off. If it's a rear wheel vehicle, the rotor is often integral to the wheel bearing and hub. For a rear wheel caliper, just pull the center wheel bearing cotter pin, nut, remove the wheel bearings and pull the rotor.