Register a Space to use GreenPepper
The plugin will alert you when a Space is actually not registered as a GreenPepper project.
Responding Yes to this question will register the current Space as a new GreenPepper project. You then will need to add your System Under Tests using the plugin configuration screens under the Project Management tab.
Un-register a Space
To un-register a Space, simply delete the XWiki object XWiki.GreenPepperSpaceClass associated to the main page of the Space.