Add Captions to Media You Share via Google Glass
Add a caption in one of two ways.
Tap the touchpad after you tell Glass the contact, Google+ circle, or social network (such as Facebook) with which you want to share your picture or video.
When you share a picture or video from your timeline, you see a message at the bottom of the screen, as shown. This text informs you that you can speak commands, so the other way you can add a caption is to say OK Glass, add caption.
When the Caption screen appears, say what you want to include in the caption.
As you speak, the words appear onscreen so that you can see what the caption will look like. You can include hashtags, if you want.