@dave r said:

... I for one would be reluctant to trust the safety of my skin to a hang glider that was designed only with SketchUp.

Right, indeed,
lol

So, Partners,
Since I solved the first problems with your helps(see my problem with Plugins folder), I would like asking the following.
I like SketchUp because it is simple and intuitive, comparing to the CAD I know. But, sketchUp designed mainly for building buildings, landscape etc. And I am building kind of a hang glider. So I need “SketchUp” for Mechanical Engineering job. For example, in Google SketchUp I may find the area and volume of my parts, but I have do additional work for finding weight, Center of Gravity, and others staff. I hope finding some CAD as simple as SketchUp, but which is doing mechanical calculations.
Thanks

@gaieus said:

Your plugin folder already exists on your computer. Please, see this post how to install zipped plugins:
http://forums.sketchucation.com/viewtopic.php?f=323&t=35746

Thank TIG, Gaieus, Dave R and other user!
I found the folder, and successfully use C of G program. So far it work.

Thank for reply.
But I have simple questions: (1) Should I create Plugins folder, or it is already exist somewhere in my computer; (2) I create the folder Plugins on the desktop, then I extract the files into this folder; next, How I can connect Google SketchUp (free downloaded by me) with the files in Plugins?

Hi, TIG
I try loading yours CofG files, but I am a Newbie and I do not know how to do that. I loading the files into mu Desktop, but what I have to do next in order to use yours CofG?
Thanks