Training your dog to use a doggie door is simple. The most common method of training a dog to use a doggie door is really just a matter of showing the dog the dog door, then putting yourself on one side of the dog door and your dog on the other and enticing him through by calling him or holding a treat.
Of course, when he does come through, reward him with the treat and spend a few minutes petting and playing with him before repeating the exercise. Many dogs will catch on in just a few minutes. Others will take a day or two. For the slower learners, try coaxing him through the dog door from both inside and outside of the house. If he seem very confused, try propping the door open at first, then lower it when he seems to understand what it’s for. Keep the whole exercise positive, be sure not to push your dog through the dog door or otherwise turn it into an unpleasant experience, and eventually he’ll get the idea.
To read an article I published on wikihow about training your dog to use a dog door click here