There is always a story to tell, so you can write down a couple of ideas such as:
Here is where we introduce the characters and the setting of our story.
Here is where something happens... magic, a problem...!
Here is where the story wraps up and all of the problems are solved (or not! ;)).
If you need additional help for your story, you can use any of the available games and apps:
Tell me a story
Rory's Story Dice
The Storytelling Game
Once Upon a Time...