In short... you don't.

When introducing any two dogs for the first time , be sure to do it on neutral ground to both dogs and while both dogs are loosely on leashes. It is important no tto have tension in the leashes so as to not over excite the dogs. The leashes are just a safety precaution in case there is a need to separate the two dogs. It can be helpful to take both dogs on a walk together first, so that they are not only interested in meeting each other and do not get overwhelmed int he process.