How to install o2 sensor in chevy s10 pick up

Disconnect negative terminal from battery, you will need an O2 sensor socket which autozone rents if you don't have one.
unplug the wire, place the socket on the sensor and turn counter clockwise, it will be really tight then pop loose and you should be able to thread it out easily. take plastic protector cap off new one (do not touch tip!) thread the new one in and tighten it then plug it in. reconnect negative terminal.