Change font size and type

Hi all,

I’m trying to change the font type and size of the events that are placed as a widget in my right column. I found on another website that I have to adjust events.css, but I can’t find this file anywhere. Also, I noticed that the size is relative to the main font size, so when I try to adjust the size all other fonts change too.
Who can help me?

https://www.ads-software.com/plugins/the-events-calendar/