Clam the ratchet in a vice. Use a wrench i belive 1/2or9/16 put it over the handle steel part should be snug against the metal part and push it against the handle part the smack the wrench with a hammer to push the handle off.
Super easy. Boil some water. Stick the old ratchet handle in it for a few a minute or so. You might be able to pull it off with your hand at that point. If not then stick it in a vice and use a pry bar to pop it off.