I subscribed to technology@beehaw.org, so I can see the posts from here. I did it by seeing a post from my local server (infosec.pub) and going to the community and joining it.
How do I get to other places in the Fediverse, though? I’m on jerboa and want to interact with e.g., https://kbin.social/m/asklemmy@lemmy.ml/t/11331/Is-Lemmy-your-first-time-on-the-Fediverse
Jerboa search only finds communities that at least 1 person on your instance subscribed to, to find new communities from other instances easily I like to use https://browse.feddit.de/
Then when you find a community, go to the web version of your instance (don’t worry it’s (mostly) mobile friendly) and type !name@instan.ce (don’t forget the !) Then you can subscribe there. Close and reopen Jerboa and your new community will show up in the list. The Jerboa devs are working on fixing this.