1) Navigate to the Web Export account pane and create a new account.
2) Set the type to Google Sites.
3) Enter your site name. The site name can be found in the url you use to access your site. For example, if you access your site with this url:
http://sites.google.com/site/bluemangols
The site name would be bluemangols.
If you use Google Apps then you will need to include your Google Apps host domain as well. An example of using this format is example.com/bluemangols.
4) Enter your username and password and test the connection.