The Branding page allows you to customize checkout pages, on demand pages, login and sign up pages with respect to colors and fonts and the wording of certain titles.
To see your options, click Settings > then click Branding under Offerings.
Here's a list of what you can update on checkout pages.
To preview the changes you make, click on your logo at the top left of your page, then click 'your page', choose something to purchase and navigate to the checkout page.
The video below shows where to make changes and how to preview them.