On the engine side of the top radiator hose is where you will find the thermostat housing, take it off, clean off all the old gasket material, pull out the old thermostat, clean off any gasket material there, put in the new one, put on a new gasket (sometimes one would use red permatex gasket sealer to make sure it seals right) bolt it all back together put the top hose back on, fill with a 50/50 mix of anti freeze and water and you should be good to go.
