An IS story consists of scenes, events, and actions. Each scene contains a group of events. Each event contains a group of actions.
An action can enhance the current event, progress to the next event, or move to another scene. Each action has a description followed by an outcome. An action may also change or add to the scene description.
IS will automatically add a new event to a scene when an actions changes the scene description. When moving between scenes, IS will automatically remember the current state of each scene, allowing the reader to progress the story concurrently across multiple scenes.
The following tutorial gives a good example on story structure and how to write your own story: