zombiecompacter

I recently got a computer good enough to run stuff like Oblivion, and of course, I want to mod it. I have it through steam, and I have the OBSE (I've heard it works with steam now). I've downloaded a mod, but can't seem to get it to work. Where should I putting it exactly? It's a .rar file (just 1), and I put it in the Data folder, is that right?