Unable to use javascript

Hi All,

I am trying to add a small Javascript applet to a sidebar to a new post on my site.

It is an affiliate advert from Forbidden Planet (a comic book/sci-fi merchandise store: https://forbiddenplanet.com/affiliates/) that I have been given the code for after opening an affiliate account with them.

I have tried many plugins to allow me to use Javascript and/or custom sidebars with no success so far.

I have tried the code I was given on a Javascript testing page (https://w3schools.com/js/tryit.asp?filename=tryjs_events) and found that there was no problem with the scripting itself.

I have also tried the code on the main body of a test page to see if there was just a problem with it being in a sidebar but had the same problem.

I am stuck with what I can do but know there must be a way around this. Does anybody know how to overcome this?

My website, https://www.cdbrosnan.co.uk, is running on the Quintus theme.

Many thanks.