2002 Regal LS O2 sensor

I'm getting the P1133 error code which when looking it up on this website says it is the oxygen sensor and I believe it's in the front (didn't know there were two). But I can't seem to find it. Can someone please be specific as to where it is for me? And what I need to do to replace it?
Thank you guys so much. This site has saved my butt so many times. Thank you again.

The Bank 1, Sensor 1 02 sensor is the one before the CAT converter. It is located on the exhaust downpipe after the rear exhaust manifold on the rear bank of the engine.

All you need is a universal 7/8" 02 sensor removal socket tool and PBBlaster spray. The socket is available at any auto parts store like Autozone.

The P1133 DTC indicates the front 02 sensor is not switching properly. Too few lean to rich (L/R) or rich to lean (R/T) switching.