adding a second image to Lugada theme header

I am using the Lugada theme for my non-profit’s website: http://www.sixthamendment.org. (Currently under construction.) There I have an image (the blue “donate” button) on the side-bar that contains a clickable link, which is placed there using the Simple Image widget. I’d like to move that image & link to the header — replacing the search box on the upper right-hand corner.

Does anyone know how to do that? I’ve been looking around in style.css and header.php, but am not entirely certain what I’m supposed to be looking for. (I’m a beginner at this stuff.)

Thanks in advance.