River, take a look at the firestorm rules here: http://www.flamesofwar.com/Portals/0/Documents/Firestorm/Overlord/FSO-Tournament-LowRes.pdf. Starting on page 19 it gives a detailed list of which firestorm units you'll recieve in game. Other than that just bring a 1250pt list from Atlantik Wall, and then you add in the firestorm units from the PDF.
Ex. The 709th firestorm unit contains a platoon with a Cmd panzerfaust smg team, and 6x rifle/MG teams. So you add that force to your 1250 pt list for that battle.