... or rather nobody is telling you (at least not the way I was able to grasp).
Create a (or use an existing, like "shared") folder for using with GitHub.
- Magit will need to create a folder in order to clone a repository (see below)
- I didn't find a way to just connect an existing folder to a repo
Create (or use an existing GitHub repo) and copy the code-url from GitHub.
- Open your folder (see above) in Emacs and use "magit-init" (Magit will prepare your folder with anything needed for further use)
- Then, within the Magit interface (magit-status if not already open) use ´C´ to clone the existing repo (´?´ for a list of available commands inside Magit)
- Fill in a name plus the URL from above, like so: "shared/new-folder-name"
You should now be ready to "stage" "commit" and "push/pull" files from your folder.