Some first thoughts:
If his cage is on the floor, get it off the floor. Your bird cage should be somewhere safe, on a large stand, preferably. On the floor, there are drafts (you know, the floor IS the coldest part of the house because heat RISES), rodents, insects, etc that can cause harm. Also, if he is on the floor, you look like a giant to him and I would personally bite you if I was on the floor too!
Second, you took this bird out of his comfort zone. Have you ever been to a foreign country, where you don't know the language, the culture & you don't know anyone. Do you know how that feels? Well, your bird is having the same feeling. He doesn't know you. There isn't anything familiar there to comfort him.
What I suggest to you, is this: Sit by your new friend in a chair. Don't stick your hand near him--UNLESS to give food and water. Sit by your new friend and talk to him. Read a book or a magazine in a chair, by the cage. Turn the radio or television on and allow your feathered friend to watch and listen as well. Do this for a week, maybe two, so your bird becomes accustomed to you.
Eat by him. Grab some portable veggies (celery or carrot sticks, snap peas, pepper strips) and eat a few in front of him. If he seems interested, offer him one that you hadn't eaten off of yet.

Stay away from onions, rhubarb, & avocado.
I hope this has been beneficial. Good luck to you and your new friend
