Start with it dry, if for some reason he doesn't eat it (which I doubt a pet store moistened it regardless), add a little bit of water, swirl it around in the food, drain the water then give it to him. It will be softer on his teeth.
My male pup has no issues with just eating his food dry. My 9 yr old female has to have hers a little wet (as described) in order for her to eat it. If I don't do it, she'll stare at me, complain then I'll wet it for her.
Wet dog food you buy at a dog store is okay to use as well, but you have to brush the dog's teeth more frequently. Dry dog food out of a bag is much better for them