First you need to find which one is bad. After you find out which one is bad you remove the 02 sensor from the exhaust pipe with an 02 sensor socket. Then you disconnect the sesor from the electrical connector. After that you can install the new one. Be carefull it's not the easist job to do in the drive way.
If you have a 4 cylinder engine, you will have two. On a 6 cylinder, you will have four.
It depends on number of cylinders the engine has. 4 cylinder engine has 2 oxygen sensors. V6 has at least 3.
O2 sensor in the exhaust manifold near the engine
Bank 1 is the passenger side of the engine
It is located in the exhaust manifold Usually in the lower front of the engine it will have a grey wire coming from it to a plug. simply remove it and replace with a new one. Keep in mind if your O2 sensor is bad you will have a check engine light on.
You can find it next to the oxygen wire harness, sticking out of the cylinder head (right side of the engine when you are facing it).
Bank 1 should be the side of the engine cylinder #1 is on.
Oxygen sensor heater malfunction (cylinder bank #2, sensor #1)
They are screwed into the exhaust system.
If your 1988 Chevrolet Celebrity has the V6 engine the oxygen sensor is in the middle of the exhaust manifold nearest the firewall. If you have the 4 cylinder engine the oxygen sensor is located in the exhaust manifold just above the exhaust pipe flange.
Bank one is the same side of the engine as cylinder 1.
I just had to replace the front one in mine and it was located on the passenger side of the engine next to the transmission dipstick