Adding Javascript in a page

Hello! I can’t insert a Javascript html code that I have to insert in the home page of https://www.ottishdesign.com/margiviaggi.. The Javascript code I have to insert is:

<div id="welcomewidget" style="width:100%"></div>        
<script type="text/javascript" src="http://welcometravel.vcms.eu/assets/js/welcomewidget.js?agent=W1486"></script>

. How can I do? I don’t know anything about javascripts.
Thank you!