Customer display can be set up as a pin pad in the HARDWARE settings.
MENU > Setting > HARDWARE > CUSTOMER DISPLAY > PIN PAD for DISPLAY TYPE setting
To use the CUSTOMER DISPLAY as a PIN PAD, check the USE box and select PIN PAD as the DISPLAY TYPE.
To finish setting up your Customer Display as a PINPAD, please refer to Pinpad Settings:
For LOCAL PINPAD settings refer to this link; LOCAL PINPAD Settings
For SHARED PINPAD settings refer to this link; SHARED PINPAD Settings