1998 Oldsmobile Cutlass ABS /BRAKE light

Which light is on, the yellow anti-lock light, the red warning light, or both?

The yellow ABS light can come on by itself, but it will also turn on if the red light is on. If the red light is on, start by pulling up on the parking brake pedal. If that turns the red light off, the main cable is stretched and must be adjusted, or, more commonly, one of the rear cables is sticking and is only partially retracted. The ABS computer will think you're driving with the parking brake applied. That would adversely affect how the rear brakes respond to control of the hydraulic system when the computer tries to pulse them.

Next check the fluid level in the master cylinder reservoir. If it is real low, add a little, but don't fill it. The fluid can be low for one of two reasons. There is a leak that must be fixed, or the front brake pads are worn and should be inspected. When new pads are installed, the fluid will be pushed back up into the reservoir. If you fill it before that, the excess fluid will spill out and make a miserable mess.

caradiodoc

Both lights are on they came on at the same time
When I start the car all the lights illumanate (for bulb check )and then go out before I move the ABS/BRAKE light comes back on

Did you try pulling up on the parking brake pedal? Did you check the brake fluid level?