Frame + Define
Go back to the notes you made after you finished your interviews, synthesized the information and identify a challenge.
Remember, it can come from any number of places: the list of difficulties, the delights, or insights, etc. It could even come from a combination of all.
Define a need, discern a need, frame the need... in a way that you can address it in the next step.
It is okay if you need to come back and refine your challenge.
"How Might We" Method
You can also use the "How Might We" method on page 85 of the field guide. It is a mad lib in the form of a question that includes one (or more) of the insights you gained from your interviews. And, bears reference to the people or communities you'll be serving along with the context in which you will be serving them.
Please share your thoughts (approximately 300 words).