How to change a tumblr dashboard theme?

I’ve truly already followed the many steps but once i instal classy nothing happens

Tagged/how to be able to customize dashboard:
http://www.tumblr.com/tagged/how+to+customize+dashboard
The way to Customize the Dashboard:
http://niggayougay.tumblr.com/post/717531766/how-to-customize-your-dashboard
Change and Create a Tumblr Tailor-made Dashboard Track record:
http://tumblring.net/change-and-create-a-tumblr-customized-dashboard-background/

Ron.