How can I "flip" a photo so that it is a mirror image of the original?

I am a relatively new Photoshop user who is working on a couple of collages of children.   Some of the pictures I'm using have wording on them which shows up 'backwards'

when printed.    I'm trying to discover how to flip the photo creating a mirror image so that the wording prints legibly.  I just cannot seem to find the correct menu for this action.