1Password for dummies - how does this thing work?

I suggest you start with the "get started" doc: https://support.1password.com/explore/get-started/
What you ask for is the "Learn more" part, but restart from the top and neither skip step 2 nor step 4.

Only after you installed the browser extension as well as the desktop app, optionally imported existing passwords from your browser's integrated password manager, continue with "Learn more".