Reddit refugee here, still finding my feet here but enjoying the feel so far.

Can someone clarify something for me?

I’m using the Liftoff app and am registered on Sopuli.

My understanding was that once I was resisted on an instance I’d be able to comment and interact with other instances across the Fediverse?

What I’m finding is (while in app) I find a thread on lemmy.world, I try to upvote or comment but I’m told I need to log into that instance?

Have misunderstood the mechanics of Lemmy or is something else at issue?