You can post to your followers and fans on your social networks by simply selecting the social channel(s) you want to post to in Campaign Setup. This is the first page you see when you enter the campaign flow.
The channels you can post to include Facebook, Twitter and Instagram.
If you're unable to select a social channel please check that you have connected to the channel in the Settings page.
To see a short video tutorial on how to connect your social channels click here.