Unfortunately (or maybe not?), I don’t have much to say on this particular topic. I started in the scene a few weeks after my 18th birthday which is also about when I started engaging in dating and relationships so I’ve never had to introduce D/s into a pure vanilla relationship.
My first long-term live-in relationship was kinky from the start. We met online in a BDSM chatroom before we met in person and dated. We didn’t have a lot of protocols or D/s stuff specifically but the topic wasn’t new to either of us. We actually started attending the local scene together and learned a lot of new things that way. Ultimately, the D/s didn’t work out in that relationship and it ended in time but we never had to have an “I’m kinky” coming out type situation.
Since I’m non-mono, I’ve been very open about my kink and Leather life with folks who are potential dating partners just so they are aware of what my life looks like. I’ve had folks say no thank you and disappear and others think its interesting, ask questions, but no interest in participating. I decided a long time ago that any primary partner in my life would need to be queer and into power exchange at a minimum because both of these things are important to me and I find it easier to connect.