Conquest of the Horde

I never was a technical person, and it seems like I have been missing out on the addons available, like GHI. My question is simply, how do I go about getting them working Ingame, where should I place the files and so forth?

Put the unzipped folder into Public > WoW > Interface > Addons. That's all you need. YOu can enable and disable addons from the character selection screen once you have them.