new sex positions

i want to ride my boyfriend in reverse cowboy but i’ve never done it before and i’m scared i’ll mess up we’ve been together for a year and are super comfortable with eachother but but i’m afraid i’ll be bad how do i do it without messing up, also i promised him we could do anal soon and he is not passing up the opportunity but i’m scared how bad will it hurt? do i need to be worried about something? hell