there are no additional plugins showing in my context menu, any other suggestions

There are a number of them but the one I need the most right now is the Simplify contour

The ruby scripts I have downloaded are not appearing in my sketchup program. I have installed them in my plug ins folder but they do not seem to appear in my pull menus in sketchup. Does anyone have any suggestions in what I can do to rectify this problem?

Thanks,
Christine