Gather your ideas - you could start with a brainstorm session and outline or mind map to help you form what you want to say.
Make a script and a storyboard - this is the backbone of your story even if it has no words — what is your story and how does it go? What does your story arc look like and what shape is it?
Get organized - gather images, video, data, and other digital media to support your script
Put it all together - choose what software you will use to tell your story and build it. You may want to test the software first just to make sure you know how to use it and it will do what you want it to do (or you can live with the compromises).
Revise - you may want to share it with others to get feedback, read it out loud, change a few images here and there, etc.
Share it out!
Where do I even start? Getting ideas flowing for writing fiction is a process.
Get inspired - Writing prompt generator or try a Madlibs-style plot generator