Custom sidebar plugin

Hello,

I downloaded this plugin, followed the activation process and created the sidebar…. however, when I get to the backend of the page I want to add the sidebar too, the custom sidebar to make selection is not there but what I get is the message “there are not replaceable sidebars selected. You can define what sidebar will be able for replacement in the Custom Sidebars config page”….. what is wrong? How can i resolve this?