Start by just opening it up and clicking on 'tutorial'. After that check out Options->Manage Emacs Packages and see if anything interests you. After that check out Melpa (<https://melpa.org>). Finally you can check out what other people do, for example Prot (<https://protesilaos.com/emacs/dotemacs>), you can look at Doom's source,...

You're basically about to go on a journey to a country you've never been, so my recommendation is to just read up about it and see if you find some things you want to experience.