The DigiX uses the Arduino IDE 1.6.5+ (Arduino 1.6.5r2 - NOT 1.6.6 or 1.6.7 strongly recommended)
and click OK
Note: If you already have additional URLs entered in that box, then click the button on the right of the box and enter this URL on a new line.
Digistump Package Sources: https://github.com/digistump/DigistumpArduino
Plug it in and away you go! It works like other Arduino boards, serial monitor works as well. Check out the examples as well as the other tutorials here and the “Due Only Libraries” here: http://arduino.cc/en/Reference/Libraries for some of the cool features.