Feeds are a collection of Sources and serve as an aggregate for your Posts. For example, you might have a Source for Twitter and Facebook, but you'd like your Posts shown alongside one another in order of their published date. That's where a Feed comes in to combine these Posts.
To get started, ensure you create your Sources first. Then, create a Feed, enabling any sources you'd like included.
To fetch the Posts for a feed, use craft.socialFeeds.getPosts().
{% set posts = craft.socialFeeds.getPosts('myFeedHandle') %}
{% for post in posts %}
ID: {{ post.id }}<br>
Content: {{ post.getContent() }}
{% endfor %}
Check out our guide on Rendering Posts for more.