Download the compressed, production jQuery file jquery-3.2.1.min.js here:
https://jquery.com/download/
Download and unzip jquery-ui-1.12.1.zip here:
https://jqueryui.com/
Place both the jQuery file and the unzipped jQuery UI folder in your study's graphics directory. Finally, reference both items from your survey's HTML head tag like this:
<script src="[% GraphicsPath() %]jquery-3.2.1.min.js"></script>
<script src="[% GraphicsPath() %]jquery-ui-1.12.1\jquery-ui.min.js"></script>