Hi Victoria,
Welcome to the site, I am also a new owner my guy is only about 6 months old. I know its scary at first because you feel like a new parent. First off I am no expert and there will be other people who will give you knowledgeable answers. Out of fear of pointing you in the wrong direction, I'm going to instead refer you to a couple of links.
As for a couple of the things you mentioned. First off a 20 gallon tank may be slightly large for a baby ball assuming that's what you bought. The heat should be on one side of the tank not in the center at around 90 degrees. You should have a hide on both sides of the cage. If he is a baby, he may not eat because of feeling insecure in his home. If you are feeding frozen thawed you will want to look at one of the links. Thermostat wise if you have the UTH running make sure it is hooked up to the thermostat asap. The UTH can and will overheat without it and kill your snake.

http://ball-pythons.net/forums/showt...ius)-Caresheet

http://ball-pythons.net/forums/showt...-Frozen-Thawed

http://ball-pythons.net/forums/showt...ass-tank-setup