How do I get my dog to stop barking when someones at the door or rings the doorbell?

every time it barks squirt water in its mouth and say quiet. Your dog will be quiet licking the water in her mouth and after some time your dog will get the idea and stop barking at the bell.

you need to get your dog used to being told and obeying to stay in one position then treat, slowly introduce door bell to this equation and gradually he will associate door bell with going to that position and not barking