Disposal leaks happen from three locations typically. (1) the plumber's putty has failed in the sink, (2) the pipes are loose or the seal rings are cracked, (3) a leak has developed internally, allowing water to rust out the bottom of the disposal.
You need to inspect the disposal closely with a strong light. Run water in the sink and run the disposal. Looks for the leak source. If it is #3, replace the unit. If it is #2, remove and replace the necessary pipes (p-trap is typical).
If it is #1, you need to remove the unit and clean the top flange and the sink hole. Roll the plumber's putty into a snake and apply it to the underside of the flange before you drop it into the sink hole. Re-mount the disposal. The putty should squeeze nicely around the perimeter of the flange in the sink. Clean the excess.
You can find "how-to" videos on Youtube showing the step-by-step installation. Bud's video omits the snap ring step which is essential.