Must be health tested , then hang out an evening out at a club / pub / dance hall . Have fun you just hanging out. Get her very tipsy , let them flirt and get close so she feels very comfortable, then as she is very tipsy tell her you want him to eat her pussy till she cums , nothing else , she has no obligation to do anything in return or sexual favour. Sit close with her kiss her make out with her as he touches her naked body and he eats her pussy till she cums , be close and intimate with her as he does . Then let her suck your cock as he watches and you and your wife fuck and make love as the guy sits back and jerk off and cums . Let her watch him as you and wife fuck. She will know the excitement of a third person and another guy and she will gradually get into the lifestyle.