Training an adult dog is very much similar to house training a puppy.
The same principles and techniques will work for both puppies and adults.
There are many reasons why your adult dog may be going potty in inappropriate places. And, it will depend on your dog’s past experiences with potty training as to how easy this will be.
This assumes that your dog did get some potty training as a puppy.
If not, or if you don’t know, then the only thing that will change is the time it will take.