Resizing a Region in Upfront

Hi. I would like to change the size of the header image in both the desktop version of the site as well as the responsive sizes. In the desktop, I'd like the image to shrink enough so that the nav bar shows above the fold. How do I do that?

In the responsive sizes I subbed in a different pic (have done this before with no difficulty) and now am stuck with a large white area that I cannot seem to remove. In the past I simply dragged up the yellow marker to change the region size, but now it is not working.

Thanks!