It’s easy, but there are a couple important things to remember.

First, you can only create a graphic box link from full web browser mode on a computer. It doesn’t work on mobile.

Second, you can’t create the link in a comment box. You have to select, “make my comment a story,” if you want a graphics block link in a comment.

That said, all you have to do is copy a link to any web page, including the https part, and then paste it into any Medium story you’re editing. Making sure your cursor remains at the very end of the text of the link, press the enter key. Et voila, after a few moments, the graphics block link will appear.