ZickZack, 10 months ago

Go to the relevant domain's front page (e.g https://kbin.social/d/kbin.social for kbin.social).
The URL scheme is "https://kbin.social/d/DOMAINHERE" assuming you are currently on kbin.social.
On the right in the sidebar you can see "Domain" and below that options to subscribe or to block.
Really it's the same thing as magazines, just that you generally don't visit the domain itself.