"Hey Emily, I'm a sub, how do I introduce myself to dominants"

As yourself! You're not a sub, you're a unique and wonderful individual and that's what anyone wants to know about in a relationship! Overlapping sexual tastes? Great! But that will not a relationship make. Let people get to know unadulterated uncensored you! If they like you like that I guarantee they'll wonder how much they'd like you at the end of a leash.