The social module provides helper snippets to enable the adding of facebook like, Google+ and Pinterest buttons to pages.
It also provides the tools to make use of Facebook comments via the [[social.fbAdmins]] and [[!social.fbComments]] snippets.
If you will be reading the tweets from one or more twitter accounts for display on your site then you first need to register your site application and enter your applications consumer key and secret into Settings > Twitter API.
You can register your site application by going to https://dev.twitter.com/apps/ once you've registered for an application you'll be provided with a Consumer Secret and Consumer Key, you will need to copy and past both into the Twitter API settings within the site manager.
Once you have the API keys in place it's a simple matter of adding the account names to the system, from the Dashboard select Twitter and Add Feed, complete the form and click Add Feed. It can take several minutes for the feed to start coming through.