The subtitles feature is available for an on-deman interview playbacks for Standard and Enterprise plans.
To add this option to the Standard plan HR should go to Teams section - Billing tab and mark "Add transcribe" checkbox. The subtitles option costs $10 for 1 job post.
To add the option to the Enterprise plan contact your sales manager.
The subtitles will be added to the Interview report. You can Generate a report from the Playback page - Scorecard tab. After click on the Generate report button, you will receive the report on your e-mail.