One very useful video is #6 How to Access Video and Audio Settings – 3.5 minutes This video shows how to open the Settings window and demonstrates what the Video and Audio settings do. The video was made using the Windows view of Zoom's settings, but the Mac view of the Settings is basically the same, with some things located a bit differently
ADDITIONAL NOTES:
Adjusting Zoom's volume for recording or listening
Note that my reference for these instructions is the Mac version of Zoom
I believe the PC version is similar
#1. Start Zoom
In the Zoom HOME window
(rectangle with two orange and three blue bubbles)
#2. click on "Settings" in near the upper-right corner
OR
open "Preferences" from the top bar usually left corner at the very top
(on a Mac, click "zoom.us" and scroll down to Preferences, which is second on the dropdown list)
#3. In the Settings window find and click the Audio icon (word "Audio" is below it)
(near the top-left corner)
#4. The settings for Microphone are in the bottom half of the window
#5. Note that you can select "Automatically adjust microphone settings"
by clicking the white box to the left of that label
** If you wish to control input volume manually, make sure the box is not checked
#6. For manual control of the input volume, find the label "Input Volume"
and slide the white dot along the line to control the level
#7. Note that the "Input Level" indicator shows the level of sound being detected
