If you upload your video using a desktop browser, Facebook can automatically generate or write captions for your video. Mobile devices currently do not have this option.
On the page's timeline select Photo/Video button, located beneath the Write a Post edit box.
Select Upload Photos/Video option to add video to your status. Navigate to the video in the file browser then choose Open button.
In the Video Details screen, type a descriptive title for your video. Describe your video so people will know what it's about in the edit box provided.
To open captioning options, select the Subtitles & Captions option on the right side of the screen.
Select the default video language from the drop down.
Choose Auto-generate, Write or Upload captions to your video.
Add Publishing Options as necessary and select Publish Button to publish the video.