With your armies selected, the next thing you will need to do is to set up a suitable battlefield using the wargames terrain in your collection.
Place at least D6+4 pieces of terrain upon the battlefield, choosing the pieces from your terrain collection (selecting which rules you will use to represent each piece).
Alternatively make at least D6+4 rolls on the Random Terrain Chart that follows to determine what kind of terrain your army will fight over.
Once you've determined the pieces of terrain your game will use, roll off with your opponent. Starting with the player who scored the highest, the players then alternate placing terrain pieces (or group of terrain pieces) until all the terrain has been placed on the battlefield.
Note that the Watchtower scenario specifies the first piece of terrain that should be placed. If you roll this scenario and do not have a watchtower to hand, you'll need to use a different building or roll again for a different pitched battle.