Go to the menu. Look for Sytem/Preferences/Mate Tweak. There are three tabs. One of whoch is "Desktop". If that is not the tab already open, click on it. Instide, there are several option regarding what to show on the desktop. deselcet those you do not with to appear and select those that you do wish to appear.
It looks like this:
That's it.
On the other hand if. for some inexplicable reason, Mate-Tweak is not installed on your system, run the following command in a terminal:
sudo apt-get install mate-tweak
Once, installed, follow the earlier instruction given above.