In order to comment, click on the (comment on this) to the right of the comment you want to comment on.
After you've added your comment (or you want to read comments from others), you can click on (Comments),
which appears next to (comment on this).
It's pretty easy once you've done it the first time.
Also, you can register for a user name -- which is also easy -- or comment as 'anonymous,'
although you can add your name to your message.
Good luck and thanks again.