You click join-lemmy.org and are presented with a page of information about the fediverse, links to set up a server and pictures of code...
More or less exactly what happened with me. Bounced off of Lemmy 4-5 times trying to decide on an instance and when this and Squabbles was recommended it seemed more intuitive.
Another option would be a lemmy instance becomes dominant and that hits the top SEO spot. Then most people use that to browse until they want to sign up and then either choose that or look around for others.