[Ashley V]

I would do it very slowly. Don't just throw them together. Maybe have the new one in a crate and let your older one approach the new one. When your older one is more relaxed, let your new one out. Make sure you ALWAYS give your older one the most attention and ALWAYS do it first. Have lots of treats on hand and praise good behavior. If you cannot supervise them, then do not leave them alone together, because it could get ugly. It'll all work out, just be patient! YOU also have to remain 100% calm and not nervous otherwise your older dog will sense that and react accordingly. If you are calm, firm, and loving, the interaction should go smoother.