When you open the subtitle editor for a video that has no subtitles yet, it will look as on the screenshot below:

To start transcribing the video:

1. Press TAB key to play the video.

2. Press ENTER key to add a line. A new subtitle box will appear under the video player:

3. Start typing what you hear (pressing TAB to pause and resume the video when necessary). The flyout on the right hand from the subtitle will show the number of characters in the current line:

4. If the line is growing too long, press SHIFT+ENTER to carry the remaining text over to the next line. This will insert a line break into the subtitle:

5. To start a new subtitle, press ENTER key:

Start and End in the flyout on the right hand mean start time and end time for the subtitle, respectively. The text you are typing is not timed yet, so both values are missing at this point.

6. Keep playing the video and typing the transcript. When you wish to make a break, click Save button in the top right-hand corner:

and then return back to editing (Resume editing) or close the editor (Exit) until your next subtitling session:

7. When you are done with typing, click Yes, start syncing button on the right-hand side:

8. You will now see the timeline under the video player. Press TAB to play the video and set the timeline in motion.

9. Press ARROW DOWN key when the first line of the transcript should appear on the screen.

10. Press ARROW UP to hide the subtitle line or ARROW DOWN again to display the next line.

11. When all the lines are synced, click Start reviewing button:

12. If necessary, edit the title and description for the video. Click the pencil icon next to the video title in the top left-hand corner:

This will open the dialog for modifying the title and description:

Make your changes and click Done to close the dialog.

13. After you've replayed the subtitled video and made sure that everything looks right, click Complete button on the right-hand panel:

Congratulations! Your transcript is finished and marked as complete. The dialog will close and you will be taken to the video page.