If we think back to the design thinking model:
The lesson plan / storyboard becomes your prototype and once you have defined the activities and flow of the learning experience it is time to test it. This could be a via a pilot event or testing group, the feedback gathered at this point is invaluable and can help shape the final experience.
I always find this part of the design process really scary! After investing so much time and effort into the learning solution this is the point where you can see that hard work pay off or fail.