How to customize configuration?

Hi there,
I notice that on the fancybox demo page:
https://fancyapps.com/fancybox/3/
There are a lot of additional options which are not exposed within the wordpress plugin configuration page. For example, thumbnails. How do I access those options?

I see this page:
https://fancyapps.com/fancybox/3/docs/#options
But I can’t quite figure out where in my wordpress config files I should be doing this.

Thank you!