How do you tell your partner you're a submissive female?

First, plan an evening of blow-his-mind sex where you have some scenes staged where he has complete control (ex: have handcuffs or rope ready for him to tie you up, have D/s porn playing in the background, tell him it turns you on when he takes charge in and out of the bedroom, etc...). After that, just come right out and tell him. Good luck! :)