Normally a radiator has a drain plug on the bottom. Make sure that you do this when the car is cold! Also use something to catch the ant-freeze and dispose of properly. If the coolant drains slowly, open the radiator cap on top to allow air to enter. You might find it easier to bring it to a quick lube shop. They will drain, dispose and refill your system faster and properly to specs. You will avoid losing time and getting dirty or getting burned!