New kitty

So my best friend is moving and she has to get rid of her cat so I took him for her. He normally was an outside cat, but occasionally went inside too. I just got him today and I am keeping all of his food and water and litter box in my closet so he can learn where all his stuff is, but he's making lots of noises and I can pet him a little bit but after a while he hisses at me. I understand that he probably has a million things going on his mind seeing as how I took him from his family and he has just been put in a completely new place with strangers, but is there anything I can do to help him adjust? There is also another kitty(very young like 3 months) and a dog that he will be living with and another cat outside that has anxiety and likes very few other animals. I'm not sure how to help him adjust so is there anything I can do to make him more comfortable or anything?