No need for root.
You have to unlock your bootloader. As I know, not every phone is eligible for that.
Then you have to install custom recovery on your phone (CWM for instance)
Now you can install mods. Just put .zip on sdcard and flash it via custom recovery (in CWM - install zip from sdcard)
Guides : http://forum.xda-developers.com/show....php?t=2558638