After downloading the mod, use a program such as 7zip or WinRAR to extract the main folder of the mod.
Drop that main folder of the mod to assets/mod_overrides. The assets folder is supposed to be in your game's installation folder (don't know where that is? click here). Create the folder if necessary
CAFCW: Extract into mod_overrides.
Optional Mods: Extract into mod_overrides.
The optional mods are, well, optional. However, the VK78 was built with those optional mods in mind, so download or ignore those mods as you wish.