Before bringing the new dog to your home, take all dogs to a park or other space to get acquainted. If you need to drive to get there, have a friend drive the new dog in a separate car from the older guy. Let the dogs "meet" in a neutral, public setting. It's OK if one of the dogs doesn't seem to pay attention to the other -- your goal is to introduce the dogs in public, rather than in the older dog's territory (home).
When you are ready to leave the public area, bring all dogs home at once. You should have few, if any, problems from there on.
The Rescue agency from which we adopted our third dog advised us to introduce them via this method, and it really works!