Ask HN: How to make sure I get this job

In one of my recent posts I asked about pricing for iOS development. Well I set a price and wrote a proposal and presented to this company. I am only 15 but they were impressed I think. They told me a few changes they would like to see and wanted me to revise the proposal and also create a 5 minute video explaining the proposal. I really would like to get this job and I think it could open many more doors for me. Does anyone have any tips, mainly for the video so that I could really sell them on the idea? Thank you very much!