I would suggest attending professional training for ideas or buying a book with extensive advice. It’s not a simple process.
You might want to join a club, buy a book, or get a video..
Find someone who knows what they are doing. Training something wrong and having to redo it is hard, but I bet you already know that from training horses:)
Sit in a hallway with your dog. Make sure all doors are closed so he will have no choice but to exit with his treasure right past you. Have him sit by you even if you have to hold him down, and roll the ball. If he is typical he will quiver at the prospect of running for it. As you give the command to “fetch” let him go for it. As he tries to escape with his treasure stop him and praise him to the skies as if it had been his idea to retrieve the ball to you. For a young dog this will become a favorite game. Use tennis balls so your dog will get used to some texture in his mouth. You can also purchase pheasant or grouse scent in a bottle like perfume. It stinks but really excites the pup. Put some on the ball and hold it to his nose before rolling the ball down the hall.
If your dog isn’t interested in chasing the ball you’ve got a wonderful pet that lacks the proper breeding to be interested in hunting. Just love him and accept him the way he is.