Good day to you,
Your theme is a premium theme and we Volunteers answering questions on this forum have no knowledge of how they are designed to operate. When you purchased your premium theme what came with that purchase was support directly from the theme designer in the Premium Theme Support Forum. There is a link for the specific Premium Theme support forum under Appearance -> Themes in your blog’s Dashboard
There is no header per say. Features include: custom typography (fonts), custom background image or colors, featured post slider, and built in featured images.
Featured Post Slider
Featured images sizes are 652 by 300 for large image in featured slider, 300 by 225 for normal post thumbnail, and 95 by 95 for small thumbnails in the index view.
Showcase top posts on your front page by enabling the featured post slider under Appearance → Theme Options. From there you can turn on autostart, change the start delay, and adjust the slide animation speed. To add a post to the slider, simply mark it as Sticky in the post’s visibility settings.
Linen theme description > http://theme.wordpress.com/themes/linen/
Linen live demo site > http://linendemo.wordpress.com/
Linen forum threads > http://en.forums.wordpress.com/tags/linen