Before making repairs, unplug the garbage disposer or shut off the power at the fuse box or breaker panel to avoid injury.
Turn off the disposer. Reach under the sink to the disposer and feel for a small, slightly recessed button. The button may be on the bottom or the side of the unit. Press the button all the way in. Now plug the disposer back into the outlet or turn on the breaker and turn on the disposer.
If it runs, job done. If it hums, it is jammed, read on. If it makes no sound at all it may be jammed or there may be another problem. First, check if the circuit breaker tripped or the fuse blew. Next, test the outlet to make sure you are getting power. If you are getting power, unplug the disposer and check the electrical connections of the cord to the appliance. If it all checks out, the motor may be burned out and you will have to replace the motor or the entire disposer.