I get asked a lot about my set up for off camera flash when I do my shoots. So I'm posting a production shot from my workshop in DC that shows me holding that exact configuration. In this shot you see in my right hand my Nikon D800 with a Pocket Wizard attached to the hot shoe (where the flash goes). In my left hand I have my Nikon Speedlight 910 with a Ray Flash attached to the end of the flash and a Pocket Wizard hooked into the bottom of the flash.
Basically by attaching the Pocket Wizards as shown it remotely fires the flash. Think of it as an extension of the flash. Since one of the Pocket Wizards is hooked up to the hot shoe on the camera, and the other is hooked up to the bottom of the flash, it's as if an invisible line is drawn connecting the two. In reality the Pocket Wizards are fired by a radio frequency where they "talk" to each other which is great because they don't have to have a line of sight to trigger.
The Ray Flash is great because it equally distributes to the light which is very helpful in many situations. I also love it because I can lay it on the ground which can be very helpful when I'm running out of hands or don't have my light stand or tripod with me. Hope this helps!