Well, if I am not mistaken you have to do the following:
(assuming you have imported the sound file correctly) let's say that the audio file is named "music"...
Conditions -> Actions
1) System/On start of Layout -> Audio/Play
(Audio file)- select: music
(Loop) - choose what ever you want
(Volume) - "0" is the original volume of the sound file
(Tag) - important! give it a tag, let's say "soundtrack". Leave the quotes.
To stop the particular sound:
2) System/On end of layout -> Audio/Stop