open_in_new content_copy 
<head>
	<link rel="stylesheet" href="https://code.jquery.com/ui/1.11.2/themes/smoothness/jquery-ui.css">
...
</head>

<body>
...
<shipping-method section="bottom">
	<fieldset class="snipcart-form__set">
		<div class="snipcart-form__field">
			<div id="datepicker">
				<input class="w-input" id="datepick-res" type="text" placeholder="Select Date" name="field" required="required">
			</div>
		</div>
	</fieldset>
</shipping-method>
...
<script src="https://code.jquery.com/ui/1.11.2/jquery-ui.js"></script>
<script>
	$(document).ready(function() {
	$( "#datepick-res" ).datepicker();
	});
</script>
</body>