Follow your lower radiator hose from the radiator to where it meets the block to find the thermostat housing. You'll have to remove the clamp, hose, and two 10mm bolts to get to it. Remove the cover on the thermostat housing, look at how the thermostat and gasket sits so you'll remember, and replace.
If I forgot something, someone feel free to add. It's been a while since I did mine.
