The drain valve is on the rear right side of radiator, near the bottom. It's whitish plastic, and takes a 1/4" square drive to turn if I recall. It only turns 90° (to the left) and it then pulls out, do not attempt to turn it further than that or it will break. The coolant will drain out the bottom.
Alternately, the quicker, but much messier way is to disconnect the lower hose. Either way, you have to get under the car to do it.
