You don't, but you can subscribe to the comms on that instance from your instance here.
If they're already federated with monyet.cc, in the search bar search !(community)@(instance). Unless it's kbin, then it's @name@instance.
If not (or just in general), get the full http url and paste in your home instance search bar and then subscribe
It's so funny how reddit-side of fedi is even more uncontrollable federated exposure that I've found myself posting to monyet with more manglish and melayu grammar simply so I can signal the post isn't meant to be international readers-first 🤣