I'm not sure I understand the question completely. But if you want to set the width and height on the chart you could just set the width and height of the div that contains it and it will fill 100% of that container.
You should be able to do something like this.
<div id="container" style="width: 300px; height: 300px;"></div>
<script type="text/javascript">
$(function() {
$('#container').highcharts({ .... config options here ... });
});
</script>