Tagging People in Google+ Photos
You can tag people in your circles on anyone's photo on Google+. When you tag an individual in any photo, that individual will be notified via their Google+ notifications. They can then remove the tag or approve it, and the photo will appear with the tag of that individual's name in it.
To tag someone, follow these steps:
Click the photo you want to tag.
Click the Add Tag button.
Expand the square around the face of the individual you're trying to tag.
Type the name of the person you want to tag and select that individual in the list provided.
Google+ automatically detects faces in your photos. If you hover your mouse cursor over a face in a photo, a box appears giving you the option to Click to Name. Click that option, and you'll be able to tag the individual in that manner as well.