You would need to convert it to a .ogg file. Then just use this function script in void OnStart() of your .hps file
PlayMusic(string& asMusicFile, bool abLoop, float afVolume, float afFadeTime, int alPrio, bool abResume);
asMusicFile - the music to play + extension .ogg
abLoop - determines whether a music track should loop
afVolume - volume of the music
afFadeTime - time in seconds until music reaches full volume
alPrio - priority of the music. Note that only the music with the highest priority can be heard! 0 - highest, 1 - lower, etc
Taken from
http://wiki.frictionalgames.com/hpl2/amn...ons#player