How to enable plugin for category description

Hello. I am trying to use Collapse o Matic on category descriptions but it seems it is not working.

Here is a link to one of our categories.
http://www.machupicchu-tours-peru.com/otros-tours

The code snippet is shown like plain text. What should I do? I want to use this as a read more/less option and I don’t like to install another plugin. Thanks!

https://ww.wp.xz.cn/plugins/jquery-collapse-o-matic/