There's a few different things problems and solutions this may be. First of what OS are you on?
If all the icons disappeared including your documents, then you might be lauding into a temporary profile. In that case restart and you should see your icons again (unless there's a bigger problem with your profile).
If you caught some sort of a virus, the icons might be hidden. In this case run a virus and malware scan first. Then to unhide the icons, open explorer. In the View tab select Show hidden files. If the icons reappear right click on the icons and go into Properties. Uncheck the Hidden box under Attributes section.
If you are just missing the Computer, Recycle Bin, and User's Files icons on Windows 10 right click on the desktop and select Personalize. Select Themes (left side menu) > Desktop icon settings. Check off all the icons you are missing. For Win 8.1, 8, and 7 right click on desktop and select Personalize. On the left side menu choose Change desktop icons, and select the icons you want.