You need to remove the bracket to the alternator, and pull the short hose that is in front of the water pump. You should be able to reach the bolts to the housing for the water pump.
Be easy while breaking the bolts on all 4 corners of the housing. Make sure the engine is cool, and that the radiator is cool. Once you pull the hose, and the housing, coolant will spill out, if it is hot, you can get a serious burn. Be sure to put a catch pan under the engine, to catch any spills. You don't want to leave any antifreeze on the ground, for one- it is messy, smelly, and sticky. For two- you don't want any kitties or puppies in the area to drink it and die.
Once you get the housing off, you will see the thermostat sitting inside, make sure you notice how it is sitting when you remove it.
The bell shape should be facing you, and the spring side should be towards the engine. If it's not, then test it in boiling water to see if it will open. If it does, put it back in, because it is working. Put it back in the right way. Could save you from buying a new one, if it is clean and rust free!
If it is in bad shape, then buy a new one, with a new gasket. Try to get one with the sticky on one side. It helps to hold it in place while you put the new one on. Do not use gasket sealer or make a gasket, because you don't want to get any gunk or filaments in your water pump.
So clean off the old gasket and dry it on the surface with a clean rag. Place the gasket on and then put the thermostat in dead center. Replace the housing and bolt back on. It is just that easy. Now make sure everything is put back on snugly, so it won't leak. Pour in coolant to required level in your radiator.
It is a good idea to start your car and let it run, (outside) long enough to heat up the radiator, and let the thermostat open up. When it does, the antifreeze level will drop down, so add more or water to get it back up again.
Then you should be good to go- check under the car, around the hoses, and the thermostat area for leaks. You want to make sure it is good and dry. If no leaks exist. Your car will be ready to drive! Good luck! :D