I don't believe there is one 'right' way to start anything...a relationship/dynamic/friendship/etc. I've heard of stories where Dom asked Sub, Sub asked Dom and with me and my Daddy I don't think the words ever came out of our mouth.
I am in my first dynamic, so it's not like I have tons of experience. Actually both my Daddy and I are in our first dynamic. We started messaging on here, moved to the phone and very quickly realized there was something between us. We were friends (I guess?) for a bit, then one day we acknowledged the feelings between us. I actually did so first. We just...spent a lot of time on the phone together, then one day we stopped and asked each other if we were going to do this. We both wanted it and that was that.
I think we might be a bit different than most couples though. Our personalities and dominance/submissiveness seem to flow seamlessly, it's just...worked since we met. We've had conversations about our kinks, things we'd like to try, things we are never going to be okay with and what we expect from one another. We sorta eased into things and let it all happen naturally.
It might also have worked so well because I am naturally submissive in all aspects of my life. I don't turn it on and off, it's always who I am. Similar for him, it's who he is. He doesn't turn it on and off, he is just a dominant man. When we got together it felt like two perfectly carved puzzle pieces meeting. There was no discussing 'submission' and 'dominance' we just....were.
I probably did not help AT ALL. Sorry, that's my story though. lol
Good Luck!