Border around entire site? Background not full screen?

I’m really trying with Upfront but after changing the background on this theme, there is a border around the entire page that I can’t edit, find the details like pixel size, or even access tools for. Also the background, which I set to tile, isn’t covering the whole page. I’ve been playing around with this all night and can’t find what setting could be causing this. I’m aggravated with it. Can someone please help me? I want to be able to build my site but this isn’t going anywhere right now.