No you gotta place it in the scenario directory.
I believe its placed at galciv2/darkavatar/galciv2/data/english/scenarios
Put it in there and it will pop up in your scenario list in the ingame menu.
I also heard cari say you can put it in the mods directory, so if this doesn't work, try the mods directory.
If that doesn't work, use one of the already made scenario's in the directory i stated above and change it to your likings, thats what i did and that works for sure!