The process is the exactly same for older dogs as it is for puppies; prevent accidents from happening by using baby gates and a crate if possible, create a predictable schedule, learn to recognize your dog’s potty signals, accompany your dog outside and immediately reward for all outdoor elimination, properly clean any accidents and supervise your dog until you’re sure that he understands the rules.
Puppies would much rather play with leaves and bugs than go potty, if you aren’t there to see that you won’t know your pup needs to go back into his crate and come out again 5-10 minutes later! He will learn to sneak away, and have accidents inside. If you leave him outside for an extended period of time, chances are when you bring him back in he will need to go outside again soon or have an accident.
A training class is not there to train your dog. Its purpose is to teach you to train your dog so you will need to be committed to train your dog for short sessions (5 minutes) several times a day rather than just simply turn up for classes! This little bit of training everyday will be repaid with a lifetime of living with a well behaved dog. You will also learn to avoid problems before they begin as well as receive help to overcome any that you already have with your dog.