To sharpen the blades, combine table salt and coarse cleanser, then shove the mixture down past the baffle (that rubber thing above the blades) and run the disposal without any water. When that’s finished, run water with the disposal like normal and rinse away the residue.
The coarse mixture should sharpen your blades. Another tip: Always run cold, not warm water when running your disposal. Cold water hardens greasy substances, which makes them easier to grind, and keeps grease from sticking to the drain lines.