Deleting Cosmos:
If you were using the Cosmos installer, open it up, as if you were updating it. Go to configure. There is an option there to "Uninstall UI". Choose that. After it finishes, choose cancel. Then choose Exit. That *should* delete the entire Interface and WTF folders. If it didn't, manually go in to your WoW directory (probably something like):
C:\Program Files\World of Warcraft\Interface
and
C:\Program Files\World of Warcraft\WTF
You want to make sure that the entire Interface and WTF folders are gone.
Installing CTMod (or *just about* any other mod, for that matter, substitute names as appropriate):
Extract the files to a folder on your desktop.
Open your WoW folder. Probably:
C:\Program Files\World of Warcraft
Create in it a new folder, called Interface
Open that folder, create another one inside it, called AddOns
Make sure on both of those that you have the capitalization the same as I do ... Capital I for Interface, Capital A and O for AddOns.
Open the AddOns folder.
Copy the files from the CT_Core folder into the AddOns folder.
Your final path should look like:
C:\Program Files\World of Warcraft\Interface\AddOns\CombatStats
C:\Program Files\World of Warcraft\Interface\AddOns\CT_BagMod
C:\Program Files\World of Warcraft\Interface\AddOns\CT_BarMod
etc.
Log into game.