How does one talk his/her spouse into living Swinging Lifestyle?
More importantly, why would you want to?
Understanding that you desire to experience erotic, sexual encounters with others is quite apparent but as a couple both of you must desire same.
Talking your spouse into sharing themselves as well as his/her soul mate with others sexually is not same as talking them into pizza over chicken for dinner or a comedy over a drama flick for entertainment.
Casually bring up subject of swinging to test waters.
If a positive response is given, continue conversation sharing your desires and why you feel lifestyle is something that you both can enjoy together.
If you receive a negative response, do not push issue. A pessimistic conversation could end in confrontation and hurt feelings.
Simply drop subject and reinitiate it another time.