Method 1

Hover the pen over the Promethean flame icon, located at the top-left corner of the Promethean board itself for 1-3 seconds. You will see the flame change colors and soon hear a soft chime sound as the calibration screen appears.

Method 2

Open the start menu and go to "Promethean" and then ActivManager. You will now see the ActivManager icon in the bottom right. Right click it and then go to "Calibration" and then either 5 or 25 points.