How to introduce an older, dominant dog to a new energetic dog?

The most important thing you can do, if they do not already know each other, is to introduce them on neutral territory where neither of them has been before. That will avoid the initial "territorial" problem if one dog is brought into the new home with the other dog already there. I would suggest neutering the intact male, several weeks before the transfer if possible. A well-bred Siberian (and that could be the iffy part for you, depending on where he comes from) is not usually aggressive towards other dogs. I have had Siberians with Finnish Spitz, Norwegian Elkhounds, German Shepherd Dogs, and Belgian Malinois over a forty-year span and never had a problem. Be sure that the resident dog's schedule changes as little as possible, as the more his environment becomes disorganized the more upset he'll be. You can bring over a towel that the new dog has slept on for a sort of pre-meet 'n' greet so that the scent is familiar. A "towel exchange," with each dog getting the other's used one, is even better. If you find you need additional help, you can click on the prompt and start a consult, where we can discuss this at length. Good luck!