Web Styling in 2023

I have put CSS in the HTML Header, but I didn’t see how to connect that CSS to the page elements like I would on a web page. I have seen lots of people on the forum discuss this topic, like:

but there doesn’t appear to be any clear consensus–and little documentation that I can see (besides really impenetrable forays into WebSDK, which I am not qualified to pursue, even if I were interested). I read you could use a WebStyle name to link CSS to a page element. Is this how you do it?

Thank you
fritz