I’m not an NSHSS ambassador but to help start the discussion you should detail where you intend to publish the video. It will guide you in choosing the right format. For example, on Youtube a video shouldn’t be longer than 5 minutes whereas on Facebook it’s 2 minutes tops. If it’s on Facebook, you should put text at the beginning of your video to leverage autoplay (without sound).
Then you should detail who is the intended audience. I don’t think it’s a good idea to target more than one. This targeted audience will help you choose what message you want to deliver to this audience and how (tone, references, wording…).
Then you have to write down the message you want to pass on. If possible, try to express it in a single sentence.
I hope those few advices can help you start.