keyboard commands to Joystik C# "Object reference not set to an instance of an object"

Hello, I would like to change keyboard commands to Joystik. Unity returns the error "Object reference not set to an instance of an object"

 public class Inputer {
     public bool handbreak;
     public float vertical;
     public float horizontal;
     
      Joystick moveJoystick;
      Joystick rotateJoystick;
     
     public void SetInput() {
         //handbreak = Input.GetButton("Jump");
         vertical = moveJoystick.position.x;//Input.GetAxis("Vertical");
         horizontal = moveJoystick.position.y;//Input.GetAxis("horizontal ");
     }
 }