Human beings are also free agents, that is, we have free will, or can freely choose between options, including moral options. That is, we can freely choose to do right or wrong.
Because of our rationality, we can understand the difference between right and wrong. And, because of our rationality, we can understand moral laws which it is our duty to accept as binding.
Our freedom to choose means then that we are capable of freely acting on this knowledge. That is we can freely choose to do what is proper.