Go to action center, the button or swipe left the right edge of the screen. and just turn tablet mode off.
http://content.gcflearnfree.org/topics/257/tablet_tabletmode_off.png
the point is why would you want a desktop on a tablet? the apps will launch fullscreen and such. but of course you can turn it off whenever you want. that's what Microsoft talked about and showed for months about how if you plug your keyboard it will ask you to turn tablet mode off, and when you unattached the keyboard it would ask you if you want tablet mode on or off.
another way it's to go to File Explorer and pin desktop to the start screen and have the icon available if you need to access that folder.
you could also create its own shortcut by using explorer.exe c:\users\username\desktop and then you pin it to the taskbar. so it won't be a pinned folder on File explorer icon.