I've read that first if your unsure how two dogs are going to act when first meeting, you should first introduce them on opposite sides of a glass door, so they get used to each other, than let them see each other at a distance, then get closer, and closer. finally, let them come up to each other and smell. if one starts to look like it's about to fight, break it up before a fight can happen. this probably isn't necessary unless you know one of the dogs is bad with other dogs.you will probably just be able to let the puppy in the house immediately, and let the two dogs sniff each other. nce again, stop a fight as soon as it breaks out, or if possible, right before. sometimes, if two dogs don't like each other, they just need some time to get used to it. and if one dog growls, don't just take the other dog away, because the growling dog will feel like it scared it away. as for the dominance issue, it doesn't matter the age, as much as the energy level ( which one is naturally more dominant). it doesn't really matter as long as they know you're in charge. ps;sorry its so long!