What do I have to do to get off probation early

Make a request to your PO for a early discharge

In my state (MD) only the judge can change the expiration date of a probation since they are the ones that imposed the probation. They will not normally change the expiration date of a probation without a good reason, such as going into the military. You must also be in full compliance to get a reduction. If you have a good reason, tell the PO and they will write the judge. If they don't think it's a good enough reason, and you do, write the judge yourself.