How to introduce two pitbulls?

[Hello, Bombshell!]

My mother has a 5 ½ month old female pitbull and I am looking into getting a pitbull for myself, also a female. The pitbull I am looking to get is 1 ½ years old sweet, obiedient and gets along well with other dogs. we also have a male chihuahua who is extremely tertitorial and unfriendly. We keep him seperate from the puppy because they do not get along. he's unfriendly in general, but has never bit or attacked the puppy when around her on or off leash, and she hasn't attacked him on or off leash either. She only pounced on him. We're in the process of getting rid of the chi. Back to my question, what is the best way to introduce these two dogs and if something were to happen, how do I stop it? Thanks
Wow. You people are extremely ignorant. You blame me for the chihiahua's tempermant? He was like this when I rescued him from being put down. And as u saud, he never bit or attacked the puppy. Not even people. All he does is bark ans growl.