You have thought about your idea. You've done the research and the dream catching. You know why you want to do this and your audience. Time to put it in a fixed form. Notice I didn't say write because it isn't the only way.
You can speak it out in an audio recording. You can draw freehand or in an storyboard format
For many of us we write it out. You can just make a simple text storyboard concept.
You can stroll through the collection at Printable Paper to see if one strikes your fancy.
If you have one of the comic book creation software you could even conjure a template out of that visual format. Find whatever works for you and make it so.