Get this great tool named JSGME and use it:
http://www.subsim.com/radioroom/showthread.php?t=94651
It's the most effective app to mod a game.
Instructions on use here:
http://www.subsim.com/radioroom/show...19&postcount=7
To make things more clear, place the decompressed mod into the Mods folder created by JSGME and install it.