You have to invoke the JS file in the head of your page. Click the add code button and add the following line to the head section:
<script>Nobotonderecho.js</script>
However, I wouldn’t bother. Many browsers can disable these features quite easily, so there is little point in adding them. The basic rule is, if you don’t want people to see the source, or download your content, don’t put them on the internet in the first place.
Thank you very much for your answers, @hendon52 and @Norm.
I think the same as @hendon52, but sometimes it is difficult to convince the client.
He thinks that not everyone knows how to disable java so that the right button works again.