How to Control Your Windows 8 Tablet's Touchscreen
Double-tap the screen.
The equivalent of a mouse double-click, the double-tap involves two quick taps of your finger. Double-tap any item on the screen that you’d like to double-click on.
Example: Double-tap a desktop folder to open it. Double-tap a web page to make it larger.
On a tablet, many things can be opened by merely tapping. So, if a tap doesn’t open an item, try the double-tap, instead.