How can I add a javascript to my website?

How can I add a javascript to my website?

For example, how can I add this code into my website? I tried code snippet but it didn't work.

<script type="text/javascript" src="http://www.oil-price.net/TABLE2/gen.php?lang=en"> </script> <noscript> To get the <a href="http://www.oil-price.net">oil price</a>, please enable Javascript. </noscript>

Thank you