How to Proceed 26M/26F

Hey everyone, husband here, last night during sex I brought up how I want to see my wife with another guy, we always simulate a threesome with a dildo (either 8+ inches and skinny or a very thick 9 inch) and she’s gotten increasingly into the fantasy of it. I’ve mentioned it here and there in the past but never push the subject bc I’m not 100% sure how to not scare her off of it, she’s a lot less sexually experienced than I coming into our marriage. I don’t want a huge wall of text in my initial post so I’ll be happy to answer or elaborate for anybody that could help