Fill up the coolant up to full line. Run the car for a while, check if its still on the full line, if not refill again. Once in a while check the coolant fluid level, if the fluid is slowly going down, the water pump may possible have a small leak or is getting ready to go.
It's the one labeled WP. The serpentine belt should be at the front of the engine, right behind the radiator. It should be about mid height on the engine on the passenger side. Look for the pulley wheels and it should be easy to find.