The plugin enables any page or post author to include a Tag Cloud by using a shortcode instead of hacking theme template files.
When you write or edit the content of a page, simply include [tagcloud] (along with the brackets) whenever you want the tag cloud to be displayed. Make sure you activate the plugin before you use the shortcode.
The plugin probably has not yet been activated.
At the moment, the tag-cloud-shortcode plugin only works when used in pages. The content displayed by the plugin table probably malfunctioned if you used the shortcode in a post.