Create a storyboard to show the service or product from start to finish

1. Draw a grid
2. Choose an opening scene: how do your users find the service exists?
3. Complete the storyboard
4. Include sufficient detail that no one has to ask 'what happens next?' or 'What goes here'
5. When in doubt, take risks - don’t look for small fixed but favour risky solutions to test
6. Keep the story to 15 minutes or less

For inspiration

How to build empathy maps