The Social feature allows you to post, schedule, and track emails and social media updates posted on Facebook, Twitter, and LinkedIn.
For a complete guide on how to post your content (emails, updates) on social media, view this this page.
To add your Facebook, Twitter, and LinkedIn account into MailUp go to Settings > List settings > Social media accounts. For more info, view this page.
MailUp also offers an email sign up form for Facebook. To learn more go here.