Welcome to AA!
I believe that places like Petco have 'kits' that contain a tank and the necessary supplies to supposedly get the tank up and running. Since you already have the tank, you may be able to get some kind of discount from your LFS
if you buy all your miscellaneous equipment/supplies all at once.
You may want to pick up a copy of "The Conscientious Marine Aquarist" by Bob Fenner. IMO
, it's an excellent source of information for anyone getting into saltwater aquariums. HTH