I looked up a list of Lemmy World instances and signed up for a bunch, but how do I see everything at once in one app instead of downloading one for each instance? I am new to what the kids call "federation." Thank you.
Go to the bottom right into profile. Upper right in the profile screen you'll see a settings gear icon. Tap that, then select accounts.
From there, it should be pretty obvious. But, yeah, it would be nice if liftoff had a front facing accounts section like most of the others do. Great app though!
If you still don't like it, connect and jerboa are currently the most reliable, with thunder being only a tad behind (but otherwise excellent) with tools g or, it was the last I checked yesterday, and I haven't seen an update for it).
But, all of those support multiple accounts.
Not that you need multiple accounts. You can access all of lemmy and kbin from a single account. You just have to search for the community within an instance, and it'll get pulled in if it isn't already. But you have to search the !community@instance, or http://instance/c/community format if it isn't already showing.
Community discovery can be a bit of a pain at times, but there's lemmyexplorer that serves as a good source until lemmy itself has more time to develop
https://browse.feddit.de/ is a good way to search through all communities across all instances though. I'd search there, subscribe in the browser, then you'll see it in your app (with a refresh obviously).
It will get easier as time goes on and lemmy (and the apps for it) get more developed.