How to Control Your Windows 8 Tablet's Touchscreen
Tap the screen.
The equivalent of a mouse click, this is a quick tap and release of your finger. You can tap any item on the screen, be it a button, icon, or other bit of computer viscera. When in tight quarters, a fingertip often works better than the pad of your finger.
Example: Tap the Next button to move to the next step; tap the Charms bar’s Start button to return to the Start screen. Tap an app on the Start screen to open it.