Are you referring those Facebook, Twitter and Linkedin social network?

If yes, currently only Twitter and Linkedin possible to automatically share to their social network when submit new story in Easysocial.

But you required to setup Twitter and Linkedin app from your account and install these following Easysocial app from your site backend > Easysocial > application

https://stackideas.com/apps/item/3342-twitter-for-easysocial
https://stackideas.com/apps/item/3395-linkedin

Once user sign up via their social network in your site Easysocial, they can able to decide whether they want to automatic post to their social network when submit new story post.

By the way, it is not possible to automatically post to Facebook because Facebook doesn't allow 3rd party provider to do that, so they need to manually share it if the user want to share to their Facebook profile page.