Changing Base Font in Untitled UI Library for Webflow Components

Hi everyone, not sure where to post this question. I'm using the Untitled UI library in Webflow. I'm fairly new to Webflow but understand some basic concepts. Not sure how best to change the base font to affect all library components? I tried updating the 'Body - All Pages' class but content is still set to System. I've tried reading various parts of the https://finsweet.com/client-first/docs but couldn't quite see where I should change this. Thanks.