The first step for getting a full-page slideshow is enable the plugin. For that, you must go to the Plugin Manager (under Extensions).
In your plugin list (you can use the search for it) you will see JS Visionary (plugin) which comes disabled by default. Enable it as the first (and required step) to achieve the full-page slideshow. You can enable it by clicking on the red toggler (meaning it's disabled). After enabling it, it will turn green.
