The inlet for the cold water and the outlet for hot are usually on top of the water heater. Turn both of the valves off. For the water to drain you will need to break loose the the connections on top. There should be waterflex or unions on the pipe that you can break loose.

If you don't do this it will never drain. Make sure the connections that you break loose are on the hot water heater side of the pipe. It will probably take a while to drain it. The drain that is leaking may not be fixable, especially if it is plastic. If that is the case you will most likely break it taking it off.

The best way to solve this problem is just buy a new water heater.

Thomas