Simply import the element
<script type="text/javascript" src="../bower_components/platform/platform.js"></script>
<link rel="import" href="bower_components/sample-polymer/audio-pad.html" />
</head>
<body>
<div class="container">
<audio-pad></audio-pad>
</div>
...and pass your element an audio context and the url to your sample after the 'polymer-ready' event has fired.
window.addEventListener('polymer-ready', function(evt) {
var pad = document.querySelector('audio-pad');
var audioContext = generateAudioContext();
pad.audioContext = audioContext;
pad.url = 'path/to/your/sample.wav';
// preload the sound without playing
pad.loadSilent();
// play the sound
pad.play();
}