This feature is part of Scoop.it Business and Scoop.it Pro.
With these two Premium offers, on top of the social media accounts already connected to your profile, you can even add some more per topic.
In order to do so select a topic in "My topics" tab at the top of your Scoop.it page to be redirected to its Curate page.
Then go to Manage> Sharing Options and connect new social networks to enlarge your sharing possibilities. The next time you edit an article from your suggested content, the new post button or the bookmarklet you'll be able to choose the social media to publish it on.
You can repeat this operation for each one of your topics!