You can read and contribute to course discussions using the edX app whenever you have an internet connection. In your course, select Discussion.
At the top level of course discussions, you see categories of posts created by course staff, usually organized based on course structure. Within each category, you see lists of posts by learners. Each post has indicators to show the number of comments and responses the post has received. The number of unread comments for a post is shown until you have viewed a post.
When you view individual posts, you can add a comment or a response, or upvote a post. Posts by community TAs or course staff have a role indicator next to their username.
For more information about course discussions, see Participating in Course Discussions.