My header image and post display incorrectly

I am using theme Twenty Fifteen. Instead of the header image displaying at the top, like the theme illustration shows, the post displays on top of the header…I can’t see a way to move or edit the position of the post, and can’t edit or move the header image..what am I missing?

http://www.revisionme.com

I am trying to clean up this site…need help!

Thank you!

Sheila Gibson