first, dial the ISO setting on the flash correspond with your camera ISO setting.
#2, select an aperture setting you want to use on your flash, than
#3, dial your lens aperture correspond with your aperture setting on your flash
#4, stay within distance of the flash working range indicated on the flash
when you shooting a subject against dark/black background, close down lens aperture about 1 stop.
when you shooting a subject against light/white background, open up lens aperture about 1 stop.
hope this help.