After you add an app to your Narrative, the required parameters must be filled in before you can run it. For most apps, you will need to select the input data object(s). Other parameters may also need to be set. A red bar to the right of a field indicates that it is a required field and you have not yet entered a valid value in it. Other indicators, such as banners for errors and warnings, may appear. Read the message and hover over any icons to reveal hints. Once you have filled or corrected the field, the indicator should disappear.