Atahualpa problems

I just started using an Atahualpa theme and I’m having problems getting changing the header and adding a logo.

I know it says something like all the images are at /wordpress/wp-content/themes/atahualpa/images/header/…buttt I’m still new to this and when I add it to my site’s url I just get an error saying I need to login (but it wont direct me to a page where I can even do that).

I know it seems like a dumb question but I would really appreciate it of someone could help me.
The site is rydermanagement.biz

Thanks