Location how to replace oxygen sensor 83 olds cutlass supreme?

Start at the exhaust manifold and follow the exhaust from the manifold rearward. You will find the O2 sensors. It may be mounted right on the manifold or somewhere on the exhaust pipe. Looks like a spark plug base with a single wire attached. Unhook the wire and use a boxed end wrench to unscrew & remove/replace the sensor.