Button that plays mp3/wav sound file on laptop

Great! This is helping 8)

Now I found this example code to play a file with Minim:

/**

  • This sketch demonstrates how to play a file with Minim.

  • It's also a good example of how to draw waveforms using the sample buffers of an AudioSource.
    */

import ddf.minim.*;

Minim minim;
AudioPlayer player;

void setup()
{
size(512, 200, P3D);
minim = new Minim(this);
// load a file, give the AudioPlayer buffers that are 2048 samples long
player = minim.loadFile("marcus_kellis_theme.mp3", 2048);
// play the file
player.play();
}

void draw()
{
background(0);
stroke(255);
// draw the waveforms
// the values returned by left.get() and right.get() will be between -1 and 1,
// so we need to scale them up to see the waveform
// note that if the file is MONO, left.get() and right.get() will return the same value
for(int i = 0; i < player.bufferSize() - 1; i++)
{
float x1 = map(i, 0, player.bufferSize(), 0, width);
float x2 = map(i+1, 0, player.bufferSize(), 0, width);
line(x1, 50 + player.left.get(i)*50, x2, 50 + player.left.get(i+1)*50);
line(x1, 150 + player.right.get(i)*50, x2, 150 + player.right.get(i+1)*50);
}
}

void stop()
{
// always close Minim audio classes when you are done with them
player.close();
// always stop Minim before exiting
minim.stop();

super.stop();
}

Where can I say that it has to be triggered by a button?