Contra is a freeware modification for Command and Conquer Generals: Zero Hour real-time strategy game and one of the first mods for this game. It adds many new units as well as numerous new upgrades, new general's powers and buildings. It also adds new sounds, maps, bug fixes, enhanced graphics, and other effects, as well as three new generals.
Check the ReadMe for some extra and perhaps useful knowledge! Who knows, maybe you can find out how to start the Map that way.