2000 Civic DX 4dr O2 sensor

hi all, this is the first time i post here.\

i have a 2000 civic DX and when i took the car to the dealer to get a check up they told me that i would need to replace my O2 sensor. now i've done a little reading and still was not able to locate where the O2 sensor is on my car. can anyone help???

BTW i do not know anything about cars. i've only taking the car seat out of my car and oil changes and thast about it.

You should have two O2 sensors. One is on the exhaust manifold and one is after the cat. Depends which one is faulty.