Please look at this example. The portal is rendered in a <div> container.
<!doctype html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Portal - jQuery EasyUI</title>
<link rel="stylesheet" type="text/css" href="https://www.jeasyui.com/easyui/themes/material-blue/easyui.css">
<link rel="stylesheet" type="text/css" href="https://www.jeasyui.com/easyui/themes/icon.css">
<script type="text/javascript" src="https://www.jeasyui.com/easyui/jquery.min.js"></script>
<script type="text/javascript" src="https://www.jeasyui.com/easyui/jquery.easyui.min.js"></script>
<script type="text/javascript" src="https://www.jeasyui.com/easyui/jquery.portal.js"></script>
<script>
$(function () {
$('#pp').portal({
border: false,
fit: true
});
});
</script>
</head>
<body>
<div style="width:800px;height:400px;border:1px solid #ccc">
<div id="pp" style="position:relative">
<div style="width:40%;">
<div title="Title1" style="height:100px;padding:10px">
<p>Content1</p>
</div>
<div title="Title2" style="height:100px;padding:10px">
<p>Content1</p>
</div>
</div>
<div style="width:60%;">
<div title="Title3" style="height:100px;padding:10px">
<p>Content3</p>
</div>
<div title="Title4" style="height:100px;padding:10px">
<p>Content4</p>
</div>
</div>
</div>
</div>
</body>
</html>