1. Upload a SubRipText file after adding a video to the composer for a single specific locale. You can add captions to a video to make it accessible to a broader audience using the SubRip (.srt) file format. Closed Captions are not visible on the preview. See the Facebook Article on required format for .SRT files.
2. To have Social Studio and Facebook properly recognize the subtitle file, use this naming format when saving your SRT file: filename.[two-letter language code]_[two-letter country code].srt