YouTube: Editing Closed Captions/Subtitles on a Video
This article explains how to edit the auto-captions YouTube adds to a video.
Upload your video.
Once it’s uploaded, go to your video and click the Info & Settings button.
On the Info & Settings screen, click the Subtitles & CC tab.
Choose “English” from the “Select Language” pop-up window.
Then click the English (Automatic) button on the right side of the screen.
You will see all of the captions YouTube added to your video. Click the Edit button on the right side of the screen to fix any mistakes.
Click into each caption box to type your corrections. Your changes will save automatically when you move to the next box. Click Publish Edits to save your work.
Now the YouTube auto-captions will be replaced by your edited captions.