The "Multi-Room Music System Comparison Chart" will tell you all the types of audio sources currently supported by audio|acacia.
If there is a source you would like to use that isn't yet supported, you should make a feature request via Feature Request List - audio|acacia. You should also contact the specific music service (i.e. Spotify, Pandora, etc.) and request that they add support for their service to audio|acacia.
If the source is supported but is not automatically showing up (such as iTunes, Winamp, or Windows Media Player libraries), you should report it as a bug.
Sources that require manual setup (such as Folder Structures, Soundcard Inputs, etc.), use the System Configuration Utility to set these sources up.