I have an antique mirror, that I want to put 2 photos onto, how?

This is a perfect project for traditional decoupage. Remove the mirror from the frame and get a piece of glass cut the same size and shape as the mirror. Have the photographs photocopied. Blacken the backs of the paper photocopies. Then glue them face down onto the back of the glass. You could use the real photographs but I would suggest using copies. You have to blacken the back otherwise the back of the photograph will appear in the mirror. This is an illustration of such a project.

Check out Youtube videos on "transfers" and select a method you think might work on a mirror. Transfers involve coating the image in some way with modpodge or other product, letting it dry, and then attaching it to the substrate with more modpodge, rubbing off the paper with water when dry. There are many versions, however, and you should try to find one specifically involving mirrors.