How do I go to a community on a specific instance?

This seems like a simple question but I couldn't intuitively figure it out in the app. I'd like to go to a specific community, and maybe even subscribe. I know the instance that the community is on, however it's not on my list of saved instances. I haven't seen any posts to this community in my feed so there's no links - I just want to type the community and instance in manually. What am I missing?