You must have "Full Access" or "Limited Access - Website" permissions to edit your site.
The "Comment Stream Page Element" provides a place for users to add and reply to comments. A Comment Stream can be added to any website page by itself or placed directly under another element, such as a News Aggregator, to collect comments about that element. Users can either add a new comment or reply to an existing one.
Sign in to your site and turn on Edit Mode.
Go to the page where you want to add the element and click Add Page Element.
Scroll down and choose the Comment Stream Page Element.
Add a title, adjust the settings, and click Create This Page Element.
How to Approve Comments
If you require comment approval when creating your Comment Stream, an admin must approve each comment before it is displayed publicly.
Sign in to your site and turn on Edit Mode.
Go to the Comment Stream Page Element.
Next to the comment, click Approve.