PLEASE HELP!!!!! 96 Ford Exploror how to reset?

You have not given any information to allow people on this group to help you. We don't even know if the check engine light is on. I can only guess that someone sold you an oxygen sensor, but that did not solve your problem (it rarely does). If you want assistance from this group, take a deep breath and gather some information: what codes were stored in your computer, which of the sensors you replaced and why, engine size, mileage, any other symptoms, any previous repairs that you attempted, etc. Have it re-scanned by someone like autozone (but don't buy anything they suggest) if you don't have the original codes.