You can easily customize your CSS files without alterting the core files, and have them load automatically.
Inside of the css folder, you will see a few css files. Any file that starts with style-***.css is one of the template styles. These are automatically loaded based on the theme you select.
In order to add your CSS customizations, create a new file and name it custom.css. Here you can safely add your customizations to affect the template's design.
This video shows you how to safely customize CSS in Wright: