I think it was at YT where I learned that one of the first things to teach your pup was that YOU are the alpha. You go out the door first, you eat first, etc. I taught Wosie to sit at the door, let me go out, and then she does not come out until I say "OK". I had to use treats to teach her, but now she does it on her own. Sometimes when I am preoccupied I just go out, and then wonder where she is! She's on the other side of the door waiting for me to tell her it's OK to come out, lol!
Good luck with this one, it'll take some patience, but you can do it.