how do I replace my thermostat in my car.

if it's the 2.3L or the 3.0L engine>>just follow the TOP radiator hose, it is mounted in coolant outlet housing...get you a good 192 degree Motorcraft thermostat for the replacement.if you are having to add WATER,where is it going? should be a 50/50 mix for maximum cooling! is the cooling fan working? and don't add just plain water...