Unable to get main page to look like preview

I for the life of me cannot get my main page to look like the preview for pinboard.
Site: https://horizontowson.com/

I want to get a horizontal image where the preview shows a latte; no matter what image I change (featured image, header image, etc….) it looks like it does now; just a floating image. I’ve been playing with this for a half an hour now and am convinced there is no option to do this in the admin panel.

Am I correct; or is there a way to setup the welcome page to look just like the theme preview?