Start with watching with her, when you have sex and she's horny, porn cuckold video and look at her reaction, ask her if she would like to be the hotwife and trying more cocks other then yours; in other words act to turn her on about that lifestyle.
Boundaries and ideas to start the cuckold lifestyle for wannabe cuckold and hotwives.
Try them and let me know what do you think about:
https://xhamster.com/videos/beginning-cuckolding-boundaries-and-ideas-6465908