Instructions on uploading captions from a captioning service, i.e. CaptionSync
Access the Edit Media Page.
Click on the Captions tab.
Click Upload a captions file.
Click Browse and select an SRT
...
caption file.
Select the caption language.
Enter a label to display for the file in the caption selector.
The caption selector displays caption options in the media player.
Click Save to upload the file.
The file is added to a table on the media page's Captions tab.