How to Do It I could finally get what I’ve always wanted. Photo illustration by Slate. Photo by Getty Images Plus. How to Do It is Slate’s sex advice column.  Have a question?  Send it to Stoya and Rich here.  It’s anonymous! Dear How to Do It, I recently returned home from work unexpectedly and found my wife in bed with another woman. Although I was outwardly furious, a part of me is insanely turned on. My wife apologized profusely and said it was a one-time thing because she’s always wanted to find out what it would be like to be with another woman, and promised it would never happen again. Now I’m debating whether to see if I can talk her into a threesome with another woman, as it’s been something I’ve been fantasizing about for years. Would that be a good idea, or should we try to move on from her indiscretion? —Would Adding a Third Be a Charm? Dear Would Adding a Third Be a Charm, If your plan is to use your wife’s indiscretion to force a threesome, that’s a bad idea.…