how to add recycle bin to desktop

If having it in the Dock isn't enough, choose Utilities from the Finder's Go menu, open the Script Editor, and run:

do shell script "ln -s ~/.Trash ~/Desktop/Trash"

The link created will only work for items on the volume containing the home folder, and can be deleted like any other item.

(246758)

The Terminal command Niel posted does not rely on the Trash being visible in the Dock.

Please post a screenshot of the distal end of your Dock