Sorry: are you talking about your TV or about your (supposed) VU+ connected to your TV?
If this last one is your case, what has to do your TV to your VU+? Unless your TV remote is able to control ALSO your VU+, you need your VU+ remote to show subtitles and the way to do that may depend on the image: usually 2xAUDIO shows the subtitles of a track (if it exists).
In OBH (if it's your image, as you posted in OBH section) you may just long press YELLOW.