Board Thread:Support Requests - Getting Started/@comment-46605478-20200812211559/@comment-168424-20200812222533

So if you get a welcome message on your user talk page or message wall, then that sort of means you joined. However, you can do something (post or reply) in Discussions (https&#58;://WIKINAME.fandom.com/f) and you won't get a welcome message, but you've effectively joined the wiki via Discussions.

It's kind of complicated. I think of "joining a wiki" as when I start getting notified about a wiki, but technically there is no explicit way to "join a wiki".