It’s been a few months but there should be the “Mode” button, top left. Normally tune radio, set volume. Now switch to camera. While in camera, press/hold Mode for about 1-2 seconds. It should switch to radio. Hold Mode to switch back and forth. Don’t believe you can change volume when in camera.
2015 Thor ACE 29.3 (Traded in)
w/'15 Jeep Wrangler Unlimited toad
2019 Fleetwood Southwind 37F
2019 Ford Ranger Lariat toad