Only a site owner can create a story type. To create a new story type, the site owner should go to the story types section of the manage page. You can access this page directly at kinja.com/manage/[siteName]/storytypes e.g. kinja.com/manage/gizmodo/storytypes.
On the story type page, click the `+` icon at the right of the page. Name your story type (suggested video story type name is “Video”) and change the content type from “Standard” to “Video”.