You must have "Full Access" or "Limited Access - Website" permissions to edit your site.
If you have more than one comment stream across your site, you can create a "Comment Aggregator" to pull all the comments from the different pages and display them together in one place.
Sign in to your site and turn on Edit Mode.
Go to the page where you want to add the aggregator and click Add Page Element.
Scroll down and choose the Comment Aggregator Page Element.
Input the settings, and click Create This Page Element.