If this is your little guys first day he is probably just scared to his new surroundings. Keep taking him out to give him a chance. Sooner or later he will get the picture
Also is he drinking enough? I know with my 2 when they first came home they did nothing but sleep for a couple of days. Barely drank water, didn't eat, I had to homecook for them so they did. After they got used to our home they were fine and dandy, lol!
Feel free to ask away! There are wonderful people here on YT willing to jump in and help at the first site of the question!