Change Font Styles for Pages

I feel like I am so close to cracking this but I am missing something.

I want to change the settings for the font styles available as a drop down menu when I edit pages (Paragraph, Heading 1, 2, 3 etc..

I have the Headway theme installed (if that make a difference).

I am looking in my File Manager for the correct place within wp-content to edit the font and can not track it down. Is it a WordPress change or a change I need to make to my Theme? Not sure if I need a child theme. Can anyone provide the best way for me to make that change?

Thank you.