Using Tab to autofill credit cards and address, etc

OK - in figuring out how to autofill credit cars and my identity, addresses, I finally figured out you had to do it when Bitwarden was set on Tab option. But then I couldn’t find Tab. It’s on Bitwarden as a website and I only found it only the extension when that was frozen up on the upper Chrome tab - it was not available when I had hit the arrow to make it freestanding.

I have it working now. So I’m good, I think. But why is ony available in one of these 3 states of Bitwarden? thanks all from a novice