Videos added to the site must include closed captioning for accessibility within 5 days of publishing.
To enable captions when uploading video to YouTube select a language and YouTube will caption your video within 48 hours (it normally happens within an hour).
To edit these captions login to the appropriate account select your icon on the top right and select YouTube Studio. Once you've reached the web app click Transcriptions in the menu on the left side of the screen. Click the drop down button under the language column you should see an option named English(automatic). Selecting the link named "published" within that row will take you to several options for editing your captions.