How to have sex like a submissive male

So i recently had sex with my mistress for the first time and I was totally the dominant one, because thats the only way i know how. She loved it and so did I, but I want to be the sub in that scenario like Im supposed to be in all scenarios with her and I don't know how. I am considerably larger than her so she cant exactly throw me around. So Im drawing a blank here. How should I behave during sex with her in the future? How do subs have sex with their dommes as subs? Ill accept any answers or opinions