My very first trouble: There is no show desktop icon on my screen of OS X!!! 
Answer: Simply press F11 on your MacBook! 
Update: I found a great solution to the question how to show desktop on you Mac! Follow the link and download the application ‘show desktop‘. It’s for free! It will add a show desktop button to your dock or on the menu bar according to your preference! Same ’show desktop’ experience like a PC in a Mac style!
