Do I need to install WotLK software to play it?

So I got the WoW and Burning Crusade starter box a couple of months ago and spent many long hours letting the game patch itself up to Cataclysm. I recently bought Wrath of the Liche King and am wondering if I have to install the software the game came with or if the game will just unlock the WotLK features. I started to install the game when I thought about this, so I stopped the download and now WoW is having to patch 2.1 gb. So plz help.