
It shouldnt be too difficult. When your pup is a little more able to hang on longer for a pee, make sure he sits by the door before you open it, every time.
It shouldnt take too long for him to click that sitting by the door makes you open it!
When he starts offering that behaviour, open the door for him, even if you think he doesnt need to pee/poo. If he goes out and doesnt pee/poo then take him in again. and finally, dont encourage him to play about outside until after he has done his toilet!
I for one am not a fan of standing around in the freezing cold whilst puppy decides he wants to play for an hour!
Em