Need to add Post Tag support

I need to add support for post_tags to the CPT created by this plugin, so that we can add some of the same tags as (normal) posts on our FAQ posts.

Although I know how to add this when I am registering a CPT (or a taxonomy) I do not know exactly how to add it to a CPT that is being registered by a plugin.

Can you please provide a code snippet that I can put in my functions.php file (I’m using a child theme) that will add the ability to add Post Tags to each FAQ post I have?

Many thanks!