If you chose to use the Smart List Trigger option to specify a goal, you will need to use the Give Credit to Referrer flow step.
Once you have built your campaign and decided what action to trigger on, simply find and select the Social App that you want to give credit to the referrer to.
Make sure your social app is configured to use Smart List Trigger. See Specify Goal for Referral Offer for details.
Excellent! Any person processed by this flow step will now give credit to its referrer.