What do you do about 1989 cutlass supreme your brake lights stay on all the time?

Check the brake light switch. It's under the dash, connected to the brake pedal. If it's adjusted wrong or faulty, it could cause the brake lights to stay on. If you can use a meter and tell that the brake light switch is ok, next test the turn signal switch. Sometimes they short out and leave the brake lights on. You'll have to pull the steering wheel to do that.