Yes, you must install it first. Here is the link to download it.
Yes, you must enable it.
Please read following article.
Should be installed and enabled first.
The comments plugin lets people comment on content on your site using their Facebook account. People can choose to share their comment activity with their friends (and friends of their friends) on Facebook as well. The comments plugin also includes built-in moderation tools and social relevance ranking
We are nopCommerce Certified Developer
We are nopCommerce MVP
Our profile in nopCommerce