Can't get streaming to work using Iris

I have installed Mopidy + Iris on a RPi, latest versions of OS etc.
I use a PC browser connecting to http://RPi-IP:6680/iris/
I just managed to play mp3 files stored on the RPi.
However I simply don’t see how to configure Internet radio.
Could somebody please give me a real world example that properly explains where I need to configure what, using any radio station URL so that I can start off with a working example?

[EDIT] I finally managed to enter a valid URL into the ADD dialog of the “Now playing” screen but I don’t see how I could store that entry for later use.
First I had tried to enter URLs in the “Playlist” tab but that did not work and now I can’t get rid of these useless entries. There is no “Delete” option. Any hints?

My 2 cents:
Subscribe to TuneIn and get from there the uri’s of your preferred radio.

A simple playlist file containing the link should do the job:

EXAMPLE:
File name antenne.m3u

http://stream.antenne.de/antenne

Place the file where all the others are and you should see the playlist in iris.