How to replace the Oxygen sensors?

Do you mean you have a code for catalytic converter efficiency? If so, properly-working oxygen sensors are required to detect that problem. Replacing the sensors isn't going to solve the problem.

There's no printed replacement procedure, probably because they think it's self-explanatory. I did find the torque spec though. There's a special socket with a slot on the side to remove O2 sensors. The wires fish through that slot. When the old sensor is rusted tight, and you're not emotionally-involved with it, meaning it's going into the trash, you can cut the wires off, then use a regular deep six-point socket. New sensors commonly come with a little anti-seize compound on the threads.