Since SPListTreeViewEx Web Part is available in the SharePoint Web Part Gallery, users with the SharePoint Design or Full Control permission level can add it to the site pages. To add a SPListTreeViewEx Web Part to a page:

1. On a site page, click [Site Actions] > [Edit Page].
   
2. Select the zone where you want to insert the Web Part, click [Insert] ribbon tab, then select [Web Part] button.
   
3. Select [RedSun] > [SPListTreeViewEx Web Part], then click [Add] button.