How to use Basic authentication

Hi

I’m trying to save a basic auth prompt but after I’ve logged into the device, BW never pops up to save the login. I’ve seen https://bitwarden.com/help/basic-auth-autofill/ but it refers to working “if there is only one login item with a matching URI.”. I’m not sure what a ‘login item’ is.

Also the animation on that page doesn’t, well, animate. Tried two different browsers.
Can anyone explain how it is meant to work?