By "an off-camera flash" do you mean the ability to control flash units that are not physically connected to the flash shoe in the camera. If so the answer is on P214 of the Advanced User Guide, which I recommend you peruse.
Here is a link to the manual" c013.pdf (start.canon).
cheers, TREVOR
The mark of good photographer is less what they hold in their hand, it's more what they hold in their head;
"All the variety, all the charm, all the beauty of life is made up of light and shadow", Leo Tolstoy;
"Skill in photography is acquired by practice and not by purchase" Percy W. Harris
