Slomanka

First, what is OBSE? Second, what is Archive Invalidation, third, how do I activate the mod anyways?

I have never downloaded a mod before, and I reciently downloaded the Kvatch Rebuilt Mod. Problem is, it is not doing anything. Are there other programs that I need to download in order to actually have a mod affect my game, or what? If there is a program needed, let me know exactly what it is.