I'm surprised no one came QQing to forums about use of this. We can use it cycloned/feared/sheeped... great combo dark bargain+cataclysm when being trained by meelee/bm pets... I can't say on forums here how to use the spell because mmo champion thinks it's an exploit, even though it clearly isn't since spell is in game.
But you can google and find the command "how to cast cataclysm warlock", easy