To add a Comment, hover over the Post you want to comment on. A small Comment button should appear in the lower-right hand corner of the Post. Click on the button to pull up Comment editor, and start adding content. You can also use the Post Toolbox to add different forms of content.
If grading is enabled, the yellow bar on the bottom of the Comment editor will gradually move to the right as you type. This indicates your progress toward the word minimum for earning points from Comments. When you reach the minimum, the bar will turn green, and the number of points you will earn upon submission will appear just above the bar. To submit your Comment and earn points, click the POST COMMENT button.