Can someone help me with my broken garbage disposal?

The last time it worked, I turned it on and there was a clanking sound then it just shut off. When I turn the switch to turn it on now, it sounds like it is trying to start up but doesn't actually start up. My sink is now draining VERY slow and there is a terrible smell under the sink where the garbage disposal is. I have no skills what so ever with fixing things but can't afford to have someone come fix it for me. What could the problem be and what do I need to do to fix it??