How do you “throw it back” during sex

So I’ve had sex with this guy once and it was the first time so it was good but not the greatest. We were sexting and he’s talking about how next time he wants me to throw it back and all this BUT IVE NEVER DONE IT.

usually I have doggy where the guy is doing everything and I’ve never really fucked back. How do I move? And I also have no ass so does it matter..helppp!! 😭😭 also I’m 23, just not very experienced.