You don't, really. You could try to have some visits from the other cat ahead of time, but even then you would need to follow standard procedures for introducing two cats. I would suggest you read up on what you need to do to set the stage for when he has to cohabitate with another cat. Here are some articles that might give you some ideas on what you could ahead of time, and how to help you prepare when they are living together.
the only thing I thought of (apart from already mentioned preparation) is scent swapping, if the cat lives close by; you can bring home something that carries his scent, like blanket, etc. But this is by no means necessary at this point.
You can start practicing patience as you will need a lot of it in the introduction process