I have read the FAQ on which templates allow for the changing of image headers, and the template I am using (Ambiru) is included in the list. I also read the following question in the FAQ, which was how to upload a picture. I have uploaded the picture I want to use as my header, but all I'm able to do is just that: upload it. How do I replace the default image with an image of my own? And do I have to resize it before I do so? Help is very much appreciated.