You should be able to edit those topics by clicking on the ‘Edit this page’ links that are found at the top of each of those pages. Clicking the link will take you to the Discourse topic that is used to create the page.
The content of each of those pages can also be found in the Admin/Customize/Text Content section. Editing the topic’s content through that section doesn’t seem to have any effect on the content of the topic that is displayed. Possibly it is only used to seed the initial content of the posts.