Make him sit everytime before you take him out soon he will sit by the door when he needs to go. Also until he's used to it your going to have to take him out every hour and make him sit before every time or he'll keep going in the house and you'll get annoyed... i know my new puppy doesn't seem to get it. I do see her sitting by the door sometimes now and know shes needs to go out it just takes time.
Good Luck!
