How sure are you the shelter wasn't just lying to you to offload a troublesome cat? Did you interact with it before adoption?
Pissing hissing and scratching are signs the cat is not sociable and has a poor temperament, probably from mistreatment. The best thing to do is to give it somewhere to rest, ideally high up (windowshelf with a blanket to sit on for example) so it can feel safe. A room that nobody goes in would be good.
Food and water nearby, along with a litter tray (not near the food/water though) if its an indoor cat. He needs to get comfortable and used to his environment, so don't bug him for a few days. Don't disturb the environment too much, give him a blanket he can sleep on to get his scent on. Then start by offering / placing down food, ideally a nice wet food or some cat treats. He will begin to associate you with pleasant experiences and be more comfortable. Don't stare at him, just act chill and relax around the house, he will eventually get comfortable with your presence and may even start to sit near you or want to be petted.
It might take a bit of time.