Hello there, MariafromUSA.
It sounds like you're trying to turn on captioning in Quicktime on your Mac. The following Knowledge Base article explains how captioning works:
OS X: Using captioning features in Mavericks - Apple Support
Captions and subtitles are available from the Subtitles menu if they are included in the video you are watching. To check to see which options are available for your video, click the Subtitles button . If captions or subtitles are available, this button appears in the navigation controls you see when you move your pointer over the video.
Not all videos include caption or subtitle tracks. Check the documentation for the video you are using to see if it includes these features.
Thanks for reaching out to Apple Support Communiites.
Cheers,
Pedro.