Hope this helps someone

If you find a community you like, in my example, AITA, and want to subscribe from Lemmy.World, I think you can just use the search bar, but you can also do this:

I clicked the link to the AITA community, hosted on KBIN

On the right sidebar, I see this: @amitheasshole@kbin.social

But I am on KBIN not Lemmy.world so I cannot login and subscribe from there directly only browse

To get to it from lemmy.world or if you can't find it easily in the search bar within Lemmy,

Edit the URL to look like this: https://lemmy.world/c/amitheasshole@kbin.social

So the format is: https://lemmy.world/c/ And then after the /c/, you put in amitheasshole@kbin.social, or whatever CommunityName@Server

Now you are logged into Lemmy, looking at the community, and can subscribe.