You should see StoryChief as a layer above all your online channels as well as an easy to use dashboard to track performance.
When you change something in your CMS afterwards, these changes will not feed back into your StoryChief story. If you were then to update the story from StoryChief, the changes that you made in the CMS will be overwritten.
Editing your story in StoryChief is the only way to make sure that additional channels are up-to-date if you need up make an alteration.
Here you can find out how to edit an already published story.