Cannot get to the file directory to put in my header image

Hello
I have the bytesforall theme.
love it, but I can't get to the directory of images to put in my custom header.
The only lead I have is this directory.
/wp-content/themes/atahualpa/images/header/

when I put it in front of the admin url
http://humanresourcefullness.com/wp-...images/header/

i get forbidden or cant' find page.

Can someone please give me the correct url to upload my custom header image to?

thanks so much