As this is still a new server the communities you may want to join may not yet be shown on unilem.org. Use a site like lemmyverse to find your favourite communities. Copy the community id eg. !lemmy@lemmy.ml and paste in the search. Wait a few seconds and the community will pop up and you can subscribe. If you still need help DM me or reply in the comments.
What server are they on? Like what is after the @ symbol? lemmy.ml? lemmy.world sth else?
I don’t see an @ symbol. Your response was fast af btw. Good sign for this “instance,” I think it’s called.