Reptiles 101

So i was in vegas for the isc show. I decided to vist a local pet shop while i was there and i noticed a super skinny Savannah monitor in one of the cages i was told they were having to force feed him and he was a picky eater. i was abel to purchase the savannah for what they paid for him do to him being so skinny dose any one know anything i can do to put wait on him or anything he might eat on his own?