HELP PLEASE.

I’m currently in a lesbian relationship and my partner has been the dominant one for quite some time. She told me she wants me to try to be dominant for once and sexually please her. I’ve always been a sub in my relationships and the idea of me doing stuff makes me nervous. I try to avoid it and she thinks I don’t want to please her. Any tips on how I can be dominant if I’ve never done anything sexual to a girl? Is it scary the first time? Thanks!!