For users using an ONSCREEN device, you simply adjust the volume using the TV's remote control for turning the volume up and down.
For users using their phones to make or receive ONSCREEN calls, adjusting the volume is done on the phone itself directly.
Troubleshooting
Not getting sound out of the TV
Make sure TV is not muted by remote. When call comes in, no need to turn down the TV volume.
Make sure the microphone on the phone is on. If using headphones or bluetooth ear buds, make sure they work in speakerphone mode.
On the ONSCREEN remote, press volume up and see the display on TV shows volume is up fully.
Switch to "internal" speaker. Caregiver Tab > Settings > [Audio/Video section] Audio Output. Set to "Internal Speakers (can help with echo)"
If sound just needs to be louder, add playback boost. Caregiver Tab > Settings > [Audio/Video section] Playback Volume. Select a boost level.
Not hearing audio from device on App
Verify microphone switch is not in "mute" position. When not in call, on Caregiver Tab, there should be no "Warning: mic off icon"
If person at the TV end just speaks too softly, add record boost. Caregiver Tab > Settings > [Audio/Video section] Microphone Recording Level. Select a boost level.