Windows 8 Consumer Preview has no direct option to add My Computer on desktop. You can use shortcut key Win + E to open Explorer window in case you need to browse files quickly, but if you love to use mouse instead of keyboard to open Explorer window, here is how to add My Computer icon on Windows 8 desktop.
Right Click on a blank space in the desktop and select ‘Personalize’ option, and then choose ‘Change desktop icons’.
In the Desktop Icon Settings popup window, select the ‘Computer’ check box and click OK to save the settings. That’s ‘it.