Dog door training
A typical dog can almost certainly be trained to use a pet door. Generally, dogs are so happy to be able to go outside and inside as they please, training is a breeze.
However, your dog doesn't know what a dog door flap is at first so he or she will need to be shown how it works.
Rule number one: keep your dog relaxed and don’t frighten it. If your dog associates stress or fear with the pet door he or she may not want to go near it again. The best way to frighten your dog is to shove it through the pet door, so please resist that behaviour and be patient.