SET UP > BUTTON/DIAL SETTING (3/3) > “APERTURE RING SETTING (A)” to “Command”
Set the aperture to Auto on lens (if it has aperture control) – without this the dial doesn’t do anything / only lens aperture ring works.
Check COMMAND DIAL SETTINGS that number 1 is F (aperture)
Now you can adjust aperture with from the front command dial
Notice that you can still set aperture to auto by scrolling with front dial to the smallest aperture direction. After last available aperture the next selection is “auto”.