You buy the aftermarket electrical switch. You remove the right side scoop. Remove the OEM switch part - a few drops of antifreeze will come out. You put in the aftermarket part, then hook up the OEM wiring to the new switch. If memory serves me, it seemed like I had to make up a couple short adapter wires to attach to the aftermarket switch because I didn't want to cut/splice the OEM multi-connector.
The new switch then activates the OEM fan at a cooler temperature, and nearer the center of the temp gauge.