How to Play An Audio File

There are a number of different ways to achieve audio playback in your Storyboard project.
It just mostly depends on your filetype.

gra.audio

The gra.audio action can be used to start or stop the asynchronous playback of a WAV audio file.
Being a built-in action for Storyboard that you get out-of-the-box, this is probably the most convenient option. However, it only works for WAV audio files.

FFmpeg

The Storyboard installation directory contains additional action definitions that can be added to your project to use FFmpeg to play both video and audio. The media action template is located in your Storyboard installation root under the directory Samples/ActionDefinitions/media.sbat.
After adding these file to your project's templates directory, you will gain access to gra.media.new.audio, amongst other useful actions. Keep in mind though that currently FFmpeg only ships with support for WebM video format and Ogg Vorbis audio format.

GStreamer

Otherwise, there is always the option to use GStreamer which has a much larger codex supported library. GStreamer is simple to set up, but compared to the other options it could be considered much more work. 

For more information about GStreamer I recommend getting started with this article: 
gstreamer/gstreamer-backend crash course – Crank Software

It's worth noting that the FFmpeg and GStreamer approaches are the only ones that would enable you to have playback control (pause, resume, seek, stop, adjust volume) over your media files. So if that's important to you then you will have to go with one of those two.