Defining header image in Studio Theme

Where do I set the header image in the Studio Theme? I am trying to copy the look of at The teacher is migrating from Weebly to us because she needs some of the WordPress plugins for functionality.

Any advice on the approach to the aesthetics would be greatly appreciated. I plan to make her background image (the photo squares) the header, have the page navigation menu appear below that and then the slide show appear below that.