If you wish to turn on your favourite screensaver into a desktop backgroup,please follw the steps.
Right-click on the desktop and click on the Change Desktop Background option.
select the Screen Saver tab.
select the screen saver which you want to set as your new desktop background.
close the Desktop & Screen Saver window.
Go to Application folder > Utilities > Open Terminal Window.
In the terminal window, Copy, paste and execute the following Terminal command which is shown below:
After entering the program in the terminal window,just minimize the terminal window.