How do I post to a Discussion board?

Discussion boards are places where your instructor can stimulate conversation for the class. Your instructor will post to the board and then you'll reply to their original post. Each post on the board will have a "Reply" button, including your instructor's post. Click "Reply" on the appropriate post and you'll post to the board either to your instructor or to another classmate. 

Check out this Canvas guide on posting to a Discussion board for more detailed instructions.