Download the module from VASSAL
www.vassalengine.org/wiki/Module:Command..._Colors:_Napoleonics
2.2 - Offical Epic module
I'd get the fan extensions while you are there
Open the module in VASSAL
Run the module and start a new scenario offline
Select either empty map
choose position as observer (this is important to keep the player sides free)
Click the terrain button to open the window, and drag terrain to the map. To pick terrain on the map, hold shift and click to select
Click the units button to open the window and drag units to the map
Use the Notes window to record the scenario information and special rules
that's about it really