Hi Kathryn,
The Xadow Duino is similarly to Arduino Leonardo that the core is ATmega32u4, i think you can use the FastLed library and example. But there is a MOSFET switch on pin VLED, don’t forget to open it when use this pin to supply power.
And then you need to care about the communicate protocol between Xadow Duino and RePhone. Maybe you need to add more commands to control more variety led string.