Changing the Forum Header phpbb3

Hi friends, I've searched several times and even tried to follow one of the examples but I still haven't been able to change my header.

I found in pics management where you can change your logo, and based on one of the examples in the FAQs I uploaded a test header but now I can't find the url to that header.

First, is that the right place to upload a fullsized header?
Second, if so where do I find the url to what I just uploaded because it wasn't in the gallery anywhere.

All I am trying to do right now is change the forum header, sorry for the newbie questions here but I've spent too much time searching for the answer.

Any help would be greatly appreciated.

Thanks

Are you referring to the forum's banner/logo or the headers for categories?

I refer to it as the header, the big thing at the top of the page that holds the logo and description which is currently at the left side.  It is probably 1024 x 150px or something like that.  The whole header of the website.