If they successfully complete the program the judge puts them on probation and requires them to pay restitution to the victim and fines and costs to the county. If they fail to carry out the terms of their probation they will be sent to prison to serve out their sentence. They must report monthly to a probation officer and are subject to random drug tests. There may be other special conditions set by the judge. Probation is very difficult and about one third of the people put on probation are sent to prison ultimately.
Many young offenders complete probation and never violate the law again.
Generally it will either be paid in monthly installments from the circuit clerks office or will be paid in one lump sum after the full amount is collected. No you file them with the police if the crime happened inside a city and with the sheriff's office if it happened in the county outside the city. Generally these agencies have many cases they are working on. It is necessary for you to talk to the officer who investigated your case or one of the felony investigators. The police chief or the sheriff generally will not know all the details of the case and will have to track down the investigator and call you back, so it is best to speak with the investigator to start with.