If you're the first person to subscribe to a community from your server, what you need to do is go to the community search, switch from "Communities" to "All", then paste in the full URL (https://lemmy.ml/c/worldbuilding)
I know it's not great, but keep in mind that Lemmy just increased their userbase by 12-fold overnight and it's a 2-man dev team. This isn't some glossy corporate product, and there will be teething issues.