Check out https://lemmy.blahaj.zone/post/61827 (specifically option 2 under find-and-subscribe) for details on how to teach lemmy about a community it doesn’t known about yet.

I think kbin magazines are supposed to be subscribable from lemmy… but I’ve heard some rumors today that it’s not working great. I think kbin.social in particular is hiding behind cloudflare captchas to try to deal with overload and I’ve heard those are breaking federation. All hearsay, I could be confused… but if you can’t get it to work today it might be worth just trying again next week after things have settled a bit.