Bringing an outside dog inside includes a period of adjustment for everyone in your nest. An outside dog is unaccustomed to a potty schedule, so house-training is essential. House-training an adult dog is essentially the same as for a puppy but it usually takes less time since adults have better elimination control.
Establish a Schedule
Establishing a potty schedule is an essential part of house-training. As the dog comes to understand that he'll have the opportunity to eliminate at certain times of day, he'll learn to hold it until you take him out. His body will adjust to a routine if you'll stick closely to the schedule. It's essential to the first stage of house-training. As you would with a puppy, take your adult dog outside to potty when he wakes up in the morning, when you let him out of his crate, after each meal, and last thing at night before going to bed. Until you have learned his needs and he has learned your schedule, take him out once an hour while he's loose in the house.
Set the Dog Up for Success
Manage the situation so the dog doesn't have the opportunity to make mistakes. This includes not only a potty schedule but also the feeding schedule. Eating necessarily results in waste; by providing food at certain times, you can predict when the dog will need to eliminate. For the same reason, you may need to limit your dog's water intake so that he doesn't drink a ton right before he'll be crated or unable to go out to urinate for several hours.
Dogs digest different foods at different rates, so learn his signals that he has to go and watch for them while he's out loose. If you can't pay close attention to him, either crate him for a short time or put him on his leash and attach the other end to your waist. He won't be able to sneak off and potty in the house, and you'll be aware of any moves he makes that indicate he needs to go out.
Cue and Reward
You might find it helpful to establish a cue for elimination, such as "go potty" or "hurry up." A cue may not be necessary every day, but it can come in handy if you have to walk the dog in the rain or cold weather. While you're house-training your dog, praise him every time he potties outside; if he's having a difficult time, give him some yummy rewards such as baked liver or hot dog pieces. Reward the dog while he's going potty to ensure he makes the connection between elimination and reward.
Deal With Mistakes
Odds are, some mistakes will happen during the house-training process, and most of them will be your fault. You either weren't watching closely enough or you varied the schedule too much too soon. If you catch your dog in the act of making a mistake, give a quick interrupter sound such as "Ack!" or "Ah-ah!" Hopefully, this will stop things and give you a chance to rush the dog outside, where he will ideally resume his elimination. Praise and reward heavily for pottying outside.
If you don't catch the dog in the act, you can't do anything about it except clean it up. Dogs associate both rewards and punishment with what they're doing at the moment, not what they did 10 or 30 minutes ago. Punishing the dog after the fact will teach him that you're unreliable and untrustworthy. Use a commercial enzymatic cleaner or mix 3 parts water with 1 part white vinegar to clean up any mistakes and neutralize odors.