Training older dogs isn’t necessarily hard. But, it does however, need patience. A good place to start is leash training. An older dog that has roamed free for most of it’s life will resent being put on a leash. Teach it to accept this.
You will need a standard size leash for your dog. Don’t buy something too short, which will make him uncomfortable and want to pull away. To get him used to wearing the leash and collar make him wear it around the house.
The Next step is to train him outside. You will have to be firm but do not be harsh. Allow him to explore by your side but not on his lonesome.
Potty training older dogs isn’t as hard as you may think. If you remember the importance of positive reinforcement the rest will be a breeze.
Just be patient and consistent, and when you take him out to do his business after meals be sure it’s the same spot. If they make a mess indoors don’t react with anger or punish him. Leave him outdoors when you clean up and remove all traces of smell by spraying with deodorants. Over time your dog will learn to do his business outside the home.