The outlet in my garage won't work!I had a fridge plugged into it.now there's black smut around it how do I replace the outlet?

Sounds like that outlet was seriously overloaded. Count your blessings that you did not have a fire. Call a qualified electrician to inspect the wires before you do anything. OH and turn the breaker off that feeds that outlet please.

Black marks usually means burning.

Turn off the breaker that feeds this outlet. Remove the faceplate and the mounting screws for the yoke that is holding the female receptacle. With the outlet in your hands, check to make sure you have copper wiring.

If you have alm. Wiring, then you need to get a "CU/ALR" make and replace the outlet. If you have copper wire, then you can get a "CU"

If you have ALM. Wiring, you might as well start checking for other loose connections in the remaining outlets in you home.