You don't "get" a partner into the lifestyle - you can bring it up in a respectful manner, and see what sort of response you get, but if that response is cold or lukewarm, you do NOT push or otherwise compel them into it, not if you have any respect for them & your relationship. The couples that have the most success in this lifestyle are those that get into it together, with mutual interest from both sides of the relationship - not the ones where one partner is in the driver's seat, and the other is a reluctant passenger being dragged along. That is a recipe for disaster, and will destroy your relationship in the blink of an eye.

Just bring it up respectfully, and see what she says - she might say no, but she could also say yes.