Garbage Collection

After installing and configuring WP Super Cache the notice at the top of the page says “Garbage collection by this plugin clears out expired and old cached pages on a regular basis. Use this form to enable it.” When I click on the link it does not work. How do I activate the Garbage Collector? The Words “This Form” is a link but does not work!

http://wordpress.org/extend/plugins/cdn-sync-tool/