Make sure you are using the lastest version of Raspbian:
$ sudo apt-get update
$ sudo apt-get upgrade
Install pifacedigitalio (for Python 3 and 2) with the following command:
$ sudo apt-get install python{,3}-pifacedigitalio
Test by running the blink.py program:
$ python3 /usr/share/doc/python3-pifacedigitalio/examples/blink.py
Install python3-pifacedigital-emulator with the following command:
$ sudo apt-get install python3-pifacedigital-emulator
Start the emulator with:
$ pifacedigital-emulator
Note
You must be in an X11 session (startx).