first go to this page: http://forums.sketchucation.com/viewtopic.php?t=11212

download this file at the bottom : ToolsOnSurface 1.6c - 15 May 10.zip

you also need to go to this page : http://forums.sketchucation.com/viewtopic.php?t=17947

and download this : LibFredo6 3.4c.zip

extract evry thing in sketchup folder.