Start by locating the thermostat housing, usually connected to the engine block with bolts or screws. Drain some coolant from the radiator to prevent spillage. Remove the bolts securing the housing and carefully lift it off. Note the orientation of the old thermostat and remove it, ensuring any gasket material is also removed. Install a new thermostat and a new gasket if required, then reattach the housing and tighten the bolts to the specified torque. Refill the coolant and check for any leaks.