I'm not trying to rip you or anything, and that the best thing in this hobby is to ask questions. But you should also research fish before you buy them. Also, how big is the shark? I hope that you do know that leopards do get to be over 5-6 ft long, require cooler water, and do become very destructive. But I will help you, sharks and most other carnivores need to eat seafood. You can buy silverslides at an LFS, as well as formulas 1&2, clams, scallops, and if it isnt eating a whole lot try squid, it has a very distinct odor, which will stimulate the shark to eat. Or you could go to your grocery store and buy some pretty seafood, like shrimp, crab meat, or fish filets, but make sure that it's uncooked and hasnt been seasoned or flavored. Most sharks have a pretty slow metabolism which means they dont have to eat all the time, but for a growing leopard shark try to feed it 4-5 times a week, and give it time for the food to digest. Also, keep it's diet varried, and try to include some vegetables in it's diet. And occassionally (maybe once a month), you could give the shark a little treat in the from of a gold fish, or possible a chromis. It's alot of fun to watch and has some vitamins and such that frozen dead foods dont have. Risc will probally have more to say on the subjesct, but this is what I would recommend.
-Mark