Im joining in on the reddit ditching thing, and was kinda worried at first that i wouldnt be able to like use it the way i did reddit as it feels like a whole new place, but after engaging with posts and people and actually being a part of lemmy rather than being lurk mode all the time i was pleasantly surprised with how easy it is to become a member of the community, theres a reasonable amount of subs (or whatever the other word for em is) that fit my interests, enough linux content and shitposting for my liking, and the overall random posts made by people equally fed up with Leddit. (also i admit i used reddit a little cus there was this post on the fedora sub showing how to fix a sound issue i been having after a recent update)
To get other instances’ content in your instance go to browse.feddit.de and find some communities you want to follow. Copy their URL, then go to your search on your instance and paste the URL, give it a few seconds to find it (this is a bit buggy in my experience, sometimes you have to try a few times, click to a different page then go back to the search somtimes), then click on it and click subscribe. I recommend you do this to a lot of communities so you can start seeing a lot of stuff in your instance’s “all” section, I subscribed to multiple dozens of communities.
To get your instance searchable from others, create an account on lemmy.ml or any of the other large ones and then subscribe to your own communities. Once I did that, a day or two later I saw 1337lemmy.com pop up in browse.feddit.de.