Search for either the url or !communityname@instance in the search bar with it set to all and then you can navigate to it using a link
Ex. for ttrpg if you want the rpg community you would search for https://ttrpg.network/c/rpg in the search bar
And then you can get to it from https://programming.dev/c/rpg@ttrpg.network (make the link manually in this format)