In order to change fonts in a theme, you’ll need to know some CSS or be comfortable using an inspector. If you’re not familiar with how to use CSS inspector in Chrome, it’s super easy to use and will make finding the css classes that you’ll need when you want to change the design. Here’s a great in-depth article about this: https://www.html5rocks.com/en/tutorials/developertools/part1/
Also, this plugin helps makes working with web fonts in WordPress a little easier: https://wordpress.org/plugins/typecase/
Hope that helps!