A simple Arduino sketch that just passed data between the Arduino's hardware serial port and a Bluetooth device connected as a software serial device on pins 10 and 11.

JYMCUExample.ino

#include <SoftwareSerial.h>
#define BT_TX 10 
#define BT_RX 11
SoftwareSerial BluetoothSerial(BT_TX, BT_RX);

void setup(){
  Serial.begin(9600);
  BluetoothSerial.begin(9600);
}

void loop() {
  if (BluetoothSerial.available())
    Serial.write(BluetoothSerial.read());
  if (Serial.available())
    BluetoothSerial.write(Serial.read());
}