You have to be destro.
Type this in: ​/script PickupSpell(135533)

It will turn your cursor into the spell icon, place it on your bar and enjoy!

"Fix if it doesnt work:

Have mannoroth's fury talented!
Upon changing to KjC I first needed to wait till Cataclysm was off cd and when I did change Cataclysm was disabled."

Fix courtesy of Tronux





Confirmed hotfix.