Put a couple of bowls near the shed, and occasionally put some dry food in them, not too much at a time. Gradually move one of the bowls further away from the shed, and over time you can teach them that the food is given near the house.
If you don't want to use only dried food, kitties love crispy democrats also....
Great advice and precisely what I would do.
For the most part cats are very resilient and will eventually learn that you are their food source. They won't have much choice but to venture out. They are very instinctive animals.
Good luck!