When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
On the terms of how to, if you have a cable release, you can just open the shutter and run to a few spots and hit it with your off camera flash. Just leave your aperture high enough to not blow it out.
Or you could use pocket wizards to trigger the flashes wirelessly.