How To create Adminimal - Responsive Administration Theme ?
Adminimal has a minimal design focused on usability with a modern look. It gets out of the user's way, with design elements used to make configuring Drupal easier as opposed to fancy for its own sake. Important text is larger, buttons are color coded (save is green, delete is red), and typography is readable. It also provides an Adminimal Menu module that cleans up the admin menu and adds useful user focused shortcuts.
Extract it in sites\all\themes
Now go to admin\appearance at the bottom of the page at Administration theme Section and select Adminimal theme from select box.
Click on Save Configuration Button for applying Adminimal Theme
After applying this theme you can see the changes. Now your admin appearance would be like this.