What am I doing wrong...? (uploading header/banner)

[nerbert]

I've never had any problem uploading an image. In cPanel open the appropriate folder then click the "Upload" button at the top of the page. You should get a new window, click "Choose File" and you'll get a popup where you can navigate to the image on your computer. On rare occasions the upload fails because of some connection glitch but then you just try again. If you don't get the upload window you should contact your hosting service.