Under the sink where most garbage disposal units are found, there is a fitted screw. This screw must be tightened as due to vibrations it comes undone from time to time. This screw requires a hex key to twist and cannot be twisted by hand.
Unrepairable. The seal around the shaft of the motor, to the blades has more than likely failed. With out motor spin to throw water away, it will leak.
If your garbage disposal is leaking you may be out of luck. Most garbage disposal manufacturers do not sell replacement gaskets for their equipment. Sorry.