I watched a kelby oneKelby One lesson and per course purchased a yongnuo yn560Yongnuo YN560-txTX manual controller to trigger my Nikon SB900 off camera with a soft boxsoftbox. Do iI need to purchase something else to make this work (rf 603R-2603 II or something). New to this and didn't mention in class. I have searched everywhere trying to figure this out because it doesn't work as is with D600, SB900, and the YN560-tx 2TX II manual controller.