This tutorial shows you how to upload a caption file; it is not a tutorial on how to create a caption file. You can either Create a Caption File, or have ITServices create your captions. Please visit our Video Caption Service page if you would like to have your videos captioned by ITServices.
NOTE: In your media library, videos with captions will have a CC icon in the bottom right of the thumbnail. You don't have to worry about remembering which videos have been captioned.