1. On a post in the Stream, click 'Add class comment'.
2. Type in what you want to say and click 'Post'.
3. Your comment will appear under the post or previous comment.
Note, everyone in the class can read this type of comment.
You can also comment on materials and assignments in the Classwork tab.
The students will receive the comment as an email too. (The notification settings can be changed. See the General - Notification settings).