Cataclysm preorder?

Q u o t e:
So i preordered cata a week ago, how do i start the download for the content? i thought it was supposed to start automatically but i dont think it started

The download will usually be initiated once you have logged in and back out of the game. As Diamora indicated though you may have already picked it up without noticing. I'm not certain how to tell simply looking at your files but Diamora's advice should work. :)