97 o2 sensor code

my service engine light is on. code check shows p0136, o2 sensor circuit malfunc. bank1 sensor2. any help?

Altimas have an inline 4cyl engine. PO136 would be a code to a V engine. If you are reading the codes from a Late model year 97 Altima, recheck the stored codes. If you are working with a V engine in another model vehicle, check the harness and connections to the O2 sensor that is in or near the bank one exhaust manifold which would be front or drivers side depending on how the engine faces.

it is a late model 97. i saw the code and wrote it down when the guy at autozone did the check. what do you mean "recheck the stored codes"?
I did have an o2 sensor replaced about 3 months ago.
how do I reset the service engine light?
Thanks