Ya start by reading the stickie about care and then u can ask us question's.
But if u just got him two some day's ago, he may be still adjusting like u said..if I remember correctly, it may take some time for some Betta's to get used to their new environment. And same thing for the food, one Betta pellet a day is ok u can even give him two.. let them soak in a spoon of tank water for a few minute's before feeding, he will eat eventually..just keep offering food.
Remember to do ur required water change's and all will be good.
Welcome BTW!