OnSign TV gives you four social networks options to you display on your screen: Facebook, Twitter, YouTube and Instagram. For their content to be shown in a campaign, you need to create a specific app for each network. Go to the tab Apps, Add App, select the Social Networks category, choose the one of your preference and insert the necessary information.
Note that for Instagram and Twitter, first you need tointegrate an account to your OnSign TV account (click on your name in the upper right corner and select Settings, then on the left side menu click on Integration Accounts and + Add Integration Account, finally it will open an option for Instagram).
See also: "How does the Media Cycling App works?".