How to replace header with an image

I have portal page here:

http://helaineolen.com/index.htm

The blog itself is at:

http://helaineolen.com/blog/

I want the header on the blog page to look like the header on the portal page.

To be specific, I want the blog pages header to have author’s name in white above a blue band across the page.

Hhttp://helaineolen.com/blog/Am I right in thinking I would edit the header.php file?

What code would I replace with what code?

TIA