jay-S,
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css"> .newClass{
background-color: #FF0000;
}
</style>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<script>
$(function() {
var n = '#mySelector .myselector';
$(n).addClass('newClass');
});
</script>
</head>
<body>
<div id="mySelector">
<div class="myselector">test</div>
</div>
</body>
</html>