New kitty in da house!

[Disturbed Blu 1]

I was coming home today when I noticed a black tabby shivering in a corner of my apartment entrance. It's raining out so I took her in. I checked around the apartments to see if she belonged to anybody and nobody has claimed her. Our downstairs neighbor said they saw her last night as well. Our guess is she was abandoned. We decided to keep her over night and try to see who owns her tomorrow.

The only problem is we already have a cat. Thunderbolt (My kitty's name. ) has been hissing and she starting hissing too. We have them in seperate rooms. Does anybody know if there is a solution to them getting a long. Thunderbolt is a boy and the cat we found is a girl by the way. Any help will be nice because if can't find who she belongs to I'll keep her (if both cats get along). I personally don't trust humane societie. Thanks.