Hi,
There is no user interface on the unit it self. Its a headless server.
On your computer (not on the pi) type
http://runeaudio.local in to your browser. that will take you to the user interface.
If that doesn't work its because you don't have the Apple bonjur client installed. But you can connect over the pi's IP.
There is a few different ways to do this to find the IP, but I'm assuming that you have a screen connected to the PI so we can get it form the pi it self.
type and run: ifconfig
Find the entry on the resulting list called inet. that is your IP. Enter that in to your browser.