How do I do it?

I really love interracial porn, and I’d really love to see my wife fucked by a big black cock. We use a black dildo during sex, it’s big, black and bigger than me. And I love fucking her with it.
She has always said she would never fuck anyone else. Can anyone tell me how I get her to become a bbc slut and turn me into a cuckold. Really appreciate your help and advice on this. Thanks xx