Playing
Simply double click a station entry. It starts with your configured audio player.
In streamtuner2 you can configure different audio players for different audio formats (MP3 or OGG). In the Apps section of the settings dialog, you can associate one player with each audio file (MIME) type. Per default this is audacious, but you can use any other media player (like VLC).
Note however that some audio players will run multiple instances and won't allow simple station switching. In such situations it might be sensible to write a wrapper script, or configure special commandline arguments to your favoured audio player (e.g. "vlc --one-instance").
It's also possible to save a station entry as .m3u or .pls file, and load this manually in your player. You might even want to collect such .m3u files for archival / backup purposes.