Please forgive me I'm an old Nappy player, I'm new to this stuff, but how are the battle groups arranged(what makes up a battle group) and what does the march order represent??? I know it's in the book but where??
Battle groups (often abbreviated to "BGs") are the basic "units" of the game but they are made up of individual bases of troops. At the beginning of the game there is usually required to be an even number of bases in a BG. See pages 22-23 for more details.
By "march order" I assume you mean "Order of March". In the Order of March each BG is listed in the player's chosen order. This determines the order in which BGs are deployed, each side deplying their army in as near to quarters as possible. See pages 137-138 and 145-146 for more details (and 142-146 for what to do about ambushes and flank marches affecting the order of deployment).