Play a Soundfile ?

Hello, i´ve created a simple countdown, then i added the musiccomponent to my gameobject and now i want that when the counter reaches “0” the musicfile starts playing.
I searched the unity wiki, but i can’t find something that helps me with my problem.

Regards

if( counter == 0 )
audio.play();

But really, without any actual code or a clearer question, just go look at the very basic Unity tutorials on the website. Playing audio files is one of the very first things they have an example for.