Side Bar Widget CSS Help

I would like to change the font within the headings of my side bar. The problem is that they are within the widgets and I don’t know how to do that. I don’t want to change the font within the rest of my blog, just the headings on the side: “ABOUT”, “INSTAGRAM”, “CATEGORIES”, “RECENT POSTS”, etc. That part. Do I try and enter the CSS code within the widgets or is there a way to do it within the CSS Stylesheet Editor that will not change the font within the body of my blog?