Recommended for fresh firmware only!
Read the instructions carefully!

Can only be flashed through CWM recovery

First, make sure you have CWM recovery installed. Then follow this steps carefully:
Download the file below and put it on your sdcard
Boot into recovery mode (CWM)
Navigate with the volume button, then choose install zip from sdcard
Choose chose zip from sdcard
Select the zip file you’ve downloaded and click yes
Wait till the installation complete then reboot your phone

Download: http://forum.xda-developers.com/showthread.php?t=1248309