Rccar bluetooth joystick QUESTION

I wrote a code for an RC car, and I want to control it with a joystick in the APP INVENTOR. How do I set the block?

#include <SoftwareSerial.h>
#include <Servo.h>
Servo myServo;

int motor_pwm = 8;
int motor_pwm1 = 2;
int motor_pwm2 = 3;
int r_motor_n = 10; //PWM control Right Motor +
int r_motor_p = 11; //PWM control Right Motor -
int l_motor_p = 9; //PWM control Left Motor -
int l_motor_n = 6; //PWM control Left Motor +
int s_motor_p = 4; //PWM control Left Motor -
int s_motor_n = 5; //PWM control Left Motor +
int serv = 13;
int speedy = 255;
char incomingByte = 0; // for incoming serial data

SoftwareSerial ble ( 0, 1 );

void setup()
{
  Serial.begin ( 9600 );
  ble.begin ( 9600 );
  myServo.attach(13);
  myServo.write(0);
  pinMode(motor_pwm, 0);
  pinMode(motor_pwm1, 0);
  pinMode(motor_pwm2, 0);
  pinMode(r_motor_n, OUTPUT); //Set control pins to be outputs
  pinMode(r_motor_p, OUTPUT);
  pinMode(l_motor_p, OUTPUT);
  pinMode(l_motor_n, OUTPUT);
  pinMode(s_motor_p, OUTPUT);
  pinMode(s_motor_n, OUTPUT);
  digitalWrite(r_motor_n, LOW); //set both motors off for start-up
  digitalWrite(r_motor_p, LOW);
  digitalWrite(l_motor_p, LOW);
  digitalWrite(l_motor_n, LOW);
  digitalWrite(s_motor_p, LOW);
  digitalWrite(s_motor_n, LOW);

  Serial.begin(9600);
}
void loop()
{
  analogWrite(motor_pwm, 255);
  analogWrite(motor_pwm1, 255);
  analogWrite(motor_pwm2, 255);

  if (ble.available() > 0)
  {
    incomingByte = ble.read();
    Serial.println(incomingByte);

    switch (incomingByte)
    {
      case 'S': // control to stop the robot
        digitalWrite(r_motor_n, LOW);
        digitalWrite(r_motor_p, LOW);
        digitalWrite(l_motor_p, LOW);
        digitalWrite(l_motor_n, LOW);
        Serial.println("Stop");
        incomingByte = '*';
        break;

      case 'R': //control for right
        analogWrite(r_motor_n, speedy);
        digitalWrite(r_motor_p, LOW);
        analogWrite(l_motor_p, speedy);
        digitalWrite(l_motor_n, LOW);
        Serial.println("right");
        incomingByte = '*';
        break;


      case 'L': //control for left
        digitalWrite(r_motor_n, LOW);
        analogWrite(r_motor_p, speedy);
        digitalWrite(l_motor_p, LOW);
        analogWrite(l_motor_n, speedy);
        Serial.println("left");
        incomingByte = '*';
        break;

      case 'F': //control for forward
        analogWrite(r_motor_n, speedy);
        digitalWrite(r_motor_p, LOW);
        digitalWrite(l_motor_p, LOW);
        analogWrite(l_motor_n, speedy);
        Serial.println("forward");
        incomingByte = '*';
        break;


      case 'B': //control for backward
        digitalWrite(r_motor_n, LOW);
        analogWrite(r_motor_p, speedy);
        analogWrite(l_motor_p, speedy);
        digitalWrite(l_motor_n, LOW);
        Serial.println("back");
        incomingByte = '*';
        break;

      case 'M': //control Mopper
        digitalWrite(s_motor_n, speedy);
        analogWrite(s_motor_p, LOW);
        Serial.println("mopper on");
        incomingByte = '*';
        break;

      case 'm': //Stop Mopper
        digitalWrite(s_motor_n, LOW);
        analogWrite(s_motor_p, LOW);
        Serial.println("mopper off");
        incomingByte = '*';
        break;

      case 'U': // roller up
        myServo.write(0);
        Serial.println("roller up");
        incomingByte = '*';
        break;

      case 'u': // roller down
        myServo.write(135);
        Serial.println("roller down");
        incomingByte = '*';
        break;

      case 'a':
        speedy = 100;
        Serial.println("speed= 10");
        incomingByte = '*';
        break;

      case 'b':
        speedy = 150;
        Serial.println("speed= 25");
        incomingByte = '*';
        break;

      case 'c':
        speedy = 200;
        Serial.println("speed= 75");
        incomingByte = '*';
        break;

      case 'd':
        speedy = 255;
        Serial.println("speed= 100");
        incomingByte = '*';
        break;
    }
  }
}