Can someone help me write a quick Watch app?

I’m fairly new to Swift so I’m not sure how to do this. I’d like a Watch app that only has a button in the middle of the screen. If the use of taps on this button, one of four random audio files play.

I know how to put a button on the screen. But I don’t know how to play an audio file let alone a random file.

Any help would be very much appreciated.

Cheers