First press Menu

Then use the F5 knob/button to navigate/scroll

Scroll down to >System and press the F5 Button to select

Scroll to 501 Camera and press the F5 button to select

Then use the knobs under the monitor to navigate the menus
Use F1 and turn it till you get to the ALL ON to turn ON the cameras
Press the F1 button to turn them ALL ON

Same thing to turn Off
Turn knob till you get to ALL OFF
Press the F1 button and they should all go off