Once the plugin is enabled, use it by selecting Tools Document Statistics. A window will display the statistical information of your document, including the number of words, lines, characters, non-space characters, and the size of your file in bytes.

You can also use Document Statistics to show you information about just a portion of your document. To do this, use the mouse pointer to select the portion of text that you want to examine, and then select ToolsDocument Statistics. Gedit will display information for both your entire document, and for the portion of text that you highlighted.