There are a couple of choices when it comes to using your WiFi internet radio to play your music collection; running a music server and streaming audio. The Noxon iRadio can do either.
I use streaming to play a random selection of my music library across our home wifi network. It's possible to listen to the stream via a computer on the wlan as well as a device such as a wifi radio.
Probably the easiest way of doing this is to use WinAmp and its associated SHOUTcast software.
Installing WinAmp is straight forward enough. There are possibly better music and media players, but WinAmp is reasonably easy to set up as a streaming application.
In addition you need the SHOUTCast DSP plugin for WinAmp and SHOUTcast Server. Both come with instructions on how to associate with WinAmp. The plugin is activated from WinAmp's options menu, but the server requires a little setting up via a .txt file. The settings are all fully explained in the file, but do require careful reading.
The advantage of streaming in this way is that you can play any music file format you like - or at least have the WinAmp codec for - despite the fact that the iRadio will only play a limited number of formats. For example, the iRadio will not play .flac or .ape files, but WinAmp/SHOUTcast transcodes the stream into an .mp3, or in my case, AAC+/48kbps format for the iRadio to play.
The disadvantage of streaming is that it is not possible to effect a choice of what's played through the iRadio. The music is directed by WinAmp's playlist. However, it does mean that from time to time you rediscover the little gems hidden away in your music collection.
*See my hifi index here.