On how to use instructions from the developer originally posted on the GoLive TalkList e-mail list: http://www.listsearch.com/golivetalk.lasso?id=349413
To install it you need to decompress the archive and then drag the folder to your GoLive/Modules/Extend Scripts/ folder.
When you relaunch GoLive you will see a new Google Site Maps palette under the Window menu.
This allows you to select the files you want to include in the site map and also their relative priorities (1 is high, 0 is low) and the update frequencies of the pages you select.
You can apply the settings to multiple files and folders at once. When you're ready to generate the site map you must enter the root URL of your web site and then click the "Generate Site Map" button. That's it.
I recommend you read the Google URL above to get a feel for what Google is looking for in a site map. Although the extension should be stable it is still in a beta state, so all feedback is appreciated.