Facebook like button goes out of screen

Hi there,

I’m fairly amateur when it comes to wordpress and I’m not able to write code although I can adjust and fiddle around with it.

I’ve added the facebook plugin to a site I’m building for a non profit society

https://www.palmandcycad.org

But parts of the like button box at the bottom of the posts is opening off screen, most notably the action button.

I have this script someone suggested

.fb-like span{overflow:visible !important; width:450px !important; margin-right:-375px;}

But i have no idea where to install it in the CSS?

Brooke