I really need some help with my robo hamster. I know nothing!?

Tumbles, My male robo hamster is my second hamster. My first hamster was when I was 8. I need to know EVERYTHING about taking care of it. What it can and can't eat, how much excersise, a certain brand of food, EVERYTHING! Thanks... Lexi. Oh one more thing... He freakes out when I put my hand in his cage. What do I do about that? He is 4 months old, I got him for Christmas.