OK, I have a light kit with 2 flashes which are easy to use..BUT I'd like to use my 580exII flash as well to lighten up the white background. I use a set of Yongnuo receivers RF-602RX. I have 3 of them but would really know how to get my 580 flash to work from them as well to have that 3rd flash. I've tried and am going to try again tomorrow on my day off but I thought I'd ask today so I can put the method into action tomorrow to make sure it works..What settings do you need to have it on so it works. I tried Manual but is there something else you need to do with it?
I appreciate any advice....Please help!

I'm fine with it on camera but when its on the receiver I'm Stumped.
I'm sure it's something simple.