Two things...
First you need an [u]If-statement[/u]. If the button is pushed, call the function that plays the sound.
Second you need to put the if-statement and the call to your sound function inside the loop, so that it sits in a loop checking the button state, and whenever the button is pushed it makes a sound and then goes-back and starts the loop over.
[u]This example[/u] shows you how to check the state of a switch to turn-on an LED. Try that 1st, then add the sound-stuff.
Actually, I'd recommed that you read through the entire [u]Arduino Language Reference[/u], not just the part about if-statements. It's not that much to read, and you don't need to memorize it. You just need to get a basic idea of what an Arduino program can do.