First of all you want to quarantine the new chin in another part of the house for 30 days. That gives the new chin time to settle in, for you to get to know it, and for any illness to show itself before possibly getting pasted to your current chin.
As for the actual intros it really varies from chin to chin, there are several methods but no one fool proof way for all. If you look up intros on the forum here you should get lots of threads. Different methods include smooshing them in a carrier together and going for a drive (The idea is common trauma/event together), the cage inside a cage with a small cage inside the big one, and the slowly moving cages closer and closer together letting them get use to each other as neighbors first. I've only done the cage next to each other, and allowed playtime together. Once they were good right next to each other and playing together I then cleaned the cage they are going in before putting both in. That way can take months though.
