They should happily accept live food. Earthworms are a good staple. You can try crickets, mealworms, pillbugs, and a number of bugs you find outside. He may not readily take food if he was just captured. It's best to leave him alone to adjust.
The salamander isn't lazy. It's just not a person or a dog or a cat, etc.
Realize that:
-You just took this creature in from outside and it's likely a little traumatized at the moment. The additional stress of poking him isn't going to be good for him.
-These creatures are nocturnal. They're used to being active at night. If you've been poking him all day he's probably a little tired.
-These creatures spend most of their time underground or under rocks, so he's likely most active when you can't see him.
In essence it's similar to having a pet nightcrawler/earthworm, but it's a little more fun to watch eat and it has four legs