Turn on Subtitles or Captions on Prime Video on Connected Devices
Enable subtitles or captions during playback of a supported title on devices such as smart TVs, set top boxes and games consoles.
You will need to select the language that you wish to have subtitles or captions are displayed in before playback. On the title's Overview screen, press up then right in order to select Subtitles. If captions are available, they'll be denoted by the
During playback of a title which supports subtitles or captions, select the
icon from the playback menu. You may need to press the enter button on your remote control or similar on a games controller to access this menu.
You can also adjust the size and color of the text used for subtitles via the Subtitles Settings menu. If your device supports it, presets can also be created and selected.
Many Prime Video titles include subtitles, alternative tracks, audio descriptions, or a combination of those. The range of supported features will depend on the device you are using.
Roku devices do not support subtitle presets - those should be edited on the Settings menu on your Roku device.
Managing Subtitles on Apple TV requires alternate steps. Visit the following link for more information https://support.apple.com/HT202772