Locate the sensor. Different car models will have the sensor in a different place and may require the removal of other items to gain access. As a general rule, the oil pressure sensor will be located in the area of the oil filter. If you don't know what the sensor for your car looks like and you're sure it needs replacing, purchase the sensor first and you'll know exactly what to look for in your car.
Remove hindering parts. You may need to remove other parts that restrict access to the sensor. Since all models are different, it would be impossible to name what will have to be removed if any.
Unplug the connector cable. There is a rubber dust boot on the cable. Pull it back and push the tab that will unlock the connector. This is a good time to clean the contacts too.
Remove the oil pressure sensor. Use an open end wrench. You may need an extended handle depending on your work space. If you are doing this without changing the oil, oil may pour out of the socket, so have the new sensor ready to put in right away.
Install the new sensor. Remember not to over tighten. Next, plug the connector back in.
Replace the other parts. If you had parts that were in the way, put things back the way they were. Now it's time to fire up the car and see if the oil pressure sensor is operating the way it should.