I use a mealworm dish as well, looks like a little rock with a opening.
I use to leave my meal worms on the sand in a certain place, and my gecko always knew that when I opened his cage, that he would find food in that certain area.
When I got the dish, I cleaned out his whole cage and once done with that, I placed everything in place, put him(my gecko) in the cage.
I didnt really do anything, he discovered the dish with the mealworms and it just became a habit and he knew that "that was his new food dish".
I placed him on the small rock once, but personally, I think he thinks he discovered it on his own. When I placed him on the rock,he walked off and ignored it.
My female I recently got, did a tour around her new home and found the dish quick and it was auto to her what it was.
My advice to you is, if your leo can't find it one its own, place him on top and let him do the rest.