[Theme: Twenty Twelve] Moving Header image above the menu

start for instance with forum search ‘Twenty Twelve Moving Header image above the menu’

one of the search results:
http://wordpress.org/support/topic/how-to-move-menu-below-header-image-in-twenty-twelve-theme?replies=24

you could also browse the direct support section for the theme where you posted this topic, however not everybody posts there; or you could browse through all topic under the ‘twenty twelve’ tag

before you start with customisatons, create a child theme to work with; http://codex.wordpress.org/Child_Themes

it is not recommended to edit the default theme Twenty Twelve directly.