Do some "research" and find videos that will appeal to her; just make sure it has some sort of cuckold or hotwife component to it. Remember, you're looking for something that your wife will find interesting or erotic, not necessarily what is YOUR favorite. Then, when the time is right and she's in a sexy mood, fire up that video and let her know how hot you find that scenario to be. Not only will it help her get comfortable with the non-monogamist theme of the porn, but she'll also see how arousing the idea is to you.
