Detailed Guide how to add videos in Steemit!!
So basically you can not upload a video directly on steemit, it has to be stored somewhere online.
And that is where youtube is the answer to all your questions.
start your story.
go to youtube and copy the link of the video.
Copy that link directy into your story.
And that it is Folks wasnt hard was it? Now i think you are good to try it yourself.