How to use Visual Intelligence on macOS Golden Gate, and when it's worth it

Apple has finally brought Visual Intelligence to the Mac with macOS Golden Gate, and it is a boon when it works. Here's how to get started.
You can select a region on your Mac's screen and if it shows food, you can get nutrition details - image credit: Apple
I admit I have sometimes taken a photo of my Mac's screen and used Visual Intelligence on my iPhone to find out what I'm looking at. But as of macOS Golden Gate, I no longer need to do that because the Mac has Visual Intelligence built in.Ap