Easy. Right click on the desktop and select View menu. My favourite is Classic Icons. By default the Icons are huge even with 1900×1200 resolution.
If you are not happy with the three standard size options (Large, Medium, Classic) you can customise them even more. Select the desktop (click on it or minimise all the windows using Win-M key) then press and hold Ctrl key and scroll up/down your mouse wheel. How to do it without mouse wheel I don’t know yet