In order to change the text on cart pages you'll first want to go to Cart Settings >> Edit Text Pages as shown below.
The next page that you should see is Site Text Pages. This page is shown below.
You can click on any of the pages to edit them (eg. About Us, Terms and Conditions, etc.).
Once you find the page you want to edit. You will see the page shown below.
On this page you can edit the page name, page title, whether the page is visible, how the page is viewed, and the page html.
The page html will be the main body of the page.
