Well there’s a million things that you can do as a top but the best thing to do is to really learn what he enjoys as a bottom. Some people prefer certain types of pain stimulation and not others, or to be called certain names, to not be treated some ways, and maybe doing sexual things that aren’t typical for average penetrative sex. It’s not always easy but really try to get him to tell you about those things or maybe show you through photos or video if it’s easier. If being dominant over him makes you uncomfortable though then there’s no need to do it. If you don’t want it then he’s not going to get what he wants out of it either. So try discussing your needs and desires as well so you can find some balance. Good luck!