Just because your new dog is old enough that he should know where to potty doesn’t mean that he actually does. An adult dog has the necessary muscle control to hold it for longer periods of time, but if no one ever taught him the potty training rules then he’s the equivalent of a brand new puppy. Age should not be equated with housetraining prowess, so it’s a good idea to treat any dog new to your home as if he’s still learning the potty training ropes.
One of the biggest mistakes new puppy owners make is expecting their puppy to hold it for longer than he is physically capable. The general guideline for puppy “hold times” is that each month of age equates to an hour of “hold time,” so a two-month-old puppy can hold it for roughly two hours. There are exceptions to the rule; your puppy should be able to hold it for slightly longer period of time at night as he gets older and you pup will need potty breaks more frequently when he’s playing.
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.
You may also notice common behavior problems in your dog such as jumping up, barking, or even aggression. The best way to correct any misbehavior is to interrupt it. Shift your dog's attention to something positive. Try running through cues that your dog has mastered followed by rewards. Keep your demeanor cool and confident, and be clear about what you mean.
Many owners appear disappointed that their young puppy will not toilet when out on a walk, yet relieves itself the second it gets back home. This is because the puppy has been taught to toilet only at home (hopefully in its garden), and being creatures of habit, they often wait until they have returned home before evacuating their bladder and/ or bowels.