Serensee asked how to install addons, a fast guide here:
Step 1Download your chosen interface
Step 2Extract the files to a folder on your desktop.
Step 3Open your WoW folder. If using a PC, the typical default install path is: C:\Program Files\World of Warcraft If using a Macintosh, the typical default install path is: Macintosh Main HD (or whatever you renamed it to, if you did)/Applications/World of Warcraft
Step 4In the WoW folder, create a new folder called Interface (if it doesn’t already exist)
Step 5Open that folder, create another one inside it, called AddOns (again, if it doesn’t already exist)
Step 6Open the AddOns folder
Step 7Your final path should look like: PC: C:\Program Files\World of Warcraft\Interface\AddOns\ now. take the folder of your chosen addon, and put in into your addon folder.
Step 8Log into game. At the character select screen, there should be an "AddOns" button in the lower left corner. Click on that. If any of the mods in the list that pops up say "out of date" or some such,
choose the "Load Outdated AddOns" option.
Step 9Log the rest of the way into game, you should be up and running now.
Luminous