Microsoft Surface 3 Manuel page 6

6. Pair the optional Pen
1. Unscrew the top of the Pen and insert the battery
("+" end facing down).
2. Swipe in from the right edge of the screen, open the
Settings charm, and then tap Change PC settings
at the bottom of the screen.
3. Tap PC and devices > Bluetooth.
Swipe Bluetooth to On.
4. Press and hold the top button on the Pen until
the LED light fashes to turn on Bluetooth wireless
technology.
5. Tap Surface Pen in the list of Bluetooth devices.
Cyan Black
Pairing light
Right-click button
Top button
Eraser button