This is off the top of my head, but if you have the rig in neutral or drive you can press the CH- button on the monitor. You may have to push it a couple of times to get the display you want. If you put it in reverse, the system will change to the rear camera and you can't change the display.
2007 Fleetwood Excursion 40E
2007 Chev Classic CC LB D/A - Toad
2013 Jeep Sahara Unlimited - Backup Toad