I want to be able to add Instructions for people. When they checkout they just go to a page that says create an account. To create a username and password. I want to add a line or two on this page.
To customize this page, you would have to do it directly to your site's theme (HTML and CSS code). You can take a look at this article on how to customize your theme: http://help.thinkific.com/support/solutions/articles/216715-custom-themes-for-developers-