When you look under the hood look for the radiator, now track the top hose to the engine,(Do not tough the engine if it is hot you will get burned) where this hose end your thermostat will be under this housing. First you must drain the coolant out of the radiator. There is a wing nut no the radiator, it's on the bottom of it. Put a drip pan under the radiator then release the coolant. Then there are two nuts or bolts holding the thermostat. It may be a 13mm socket to remove the nuts. After removing the nuts the housing will come off and the thermostat is sitting under the housing. Remove and replace with the same temperature thermostat.
First and foremost make sure the car hasnt ran in a while.theres two hoses coming out of your radiator ,one goes to the water pump,the other goes to a neck thats bolted to the engine.remove these bolts.and remove the neck.the thermostat is drectly under this neck and can be removed with a scewdriver or small pry bar.I hope ive been of some help.