I know that there are probably proper ways to introduce new pups into a house with existing animals. And if I were introducing an older dog into a house with other dogs I would probably use some of those ideas. But with puppies I have always just brought them right in. I have never formally introduced the new pup to the elders. i kinda just have the mentality of 'here's your new home, your new brothers and sisters, figure it out.' It has always worked well for me doing it this way, even with Salty the grouch. I have never left the pup alone with any of them, always crated when we are gone, and i always keep an eye on their interactions but I think older dogs instinctively know that they are babies and they treat them accordingly. Also, in my particular instance since I have always had multiple animals, my guys probably think aww geez she brought another one home and they just have learned to accept it.