As Brian states, modules are bases upon which games can be built. They can't be added to existing games without first creating a game based on them and using the pro subscriber perk of the transmogrifier to move the assets over. I believe there is a suggestion to have them as added content such as the add ons but I'm not sure how viable it is given that modules are generally larger and could lead to game breaking bloat if one were to start combining them. Sorry it wasn't better news if you are wanting to add it to an existing game already in progress :/
