How to change background…and other doc

Trying this theme out in dev…kind of stumped right out of the box, as there appears to be no way to change the background – at all. There is no option in the Customize window for the background, and that window has been taken over by the theme, as opposed to having a separate theme customization page like other themes do…so I’m really at a loss.

Have looked at the theme’s homepage and don’t see any links for documentation there either…

???