Try putting the full provided link (as posted, no editing, so: https://lemmy.blahaj.zone/c/lemmy_wishlist) in search bar of your instance. This should prompt this community to start getting federated on your instance and then it should be accessible at https://lemm.ee/c/lemmy_wishlist@lemmy.blahaj.zone
I meant search page I guess. There's a magnifying glass Icon at the top of the page. You should see something like this on the Image here. And then you can subscribe to the community from your instance