To link to a community, use
![community]@[instance]
, for example [email protected]
The Jerboa app and the Lemmy Web UI will use your home instance's version of that remote community so you can interact with it.
Another way to do it is through a direct link, e.g. https://lemmy.ml/c/memes, however this is less helpful as then people on other servers can't interact with the linked content (without a lemmy.ml account in this case).