Setting a primary channel is necessary for publishing. It tells StoryChief which version of the story should be used for links (e.g. social platforms, newsletters) and also lets search engines know what the main source of that story is.
Start setting your primary channel
Step 1. Go to the story of which you like to set the primary channel.
Step 2. The primary is set in the "Audience" tab of the story. Clicking on "Set as primary" will change it to that channel.