In reply to Frank Meeuwsen.

Frank, apologies in advance to you and your readers for the reply in English. The feature is definitely in Beta and there are no instructions I'm aware of yet, but if you're adventurous and want to take a stab, you might try visiting https://threadreaderapp.com/account/micropub while logged into ThreadReader to see what happens. The developers may drop some documentation/links into the IndieWeb chat shortly for a more "official" beta, but do write about your experiences/problems so they can fix any problems or round off any UI quirks you may encounter.