How to use AT commands in serial?

Hey guys,
I have connected my arduino to the obd2 connector with pins at 0(RX), 1(TX),5v and GND.
I am trying to test this out using an OBD2 Emulator from freematics it comes with a GUI . The instructions say that
"The serial control interface is implemented as AT command-set containing following commands. The baud rate is 38400bps. All commands and responses are terminated with ‘\r’ (ASCII: 0xd). "
and has the commands below.
I cant seem to connect to the GUI. Heres my code

#include <Arduino.h>
#include <Wire.h>
#include <OBD.h>

COBDI2C obd;

void setup()
{
  // we'll use the debug LED as output
  pinMode(13, OUTPUT);  
  // start communication with OBD-II UART adapter
  obd.begin();
  // initiate OBD-II connection until success
  while (!obd.init());  
  Serial.begin(38400);                    
}

void loop()
{
  int value;
  if (obd.read(PID_RPM, value)) {
    // RPM is successfully read and its value stored in variable 'value'
    // light on LED when RPM exceeds 3000
    digitalWrite(13, value > 1000 ? HIGH : LOW);
  }
}

I don't have the device or library but didn't the library have any examples?

In your Arduino IDE, under FILE is a menu choice Examples that should give you a list of your libraries under the official example categories. If you have the OBD library in the right place and it has any examples then OBD should appear as a choice in the Examples menu and you can click it to open an example sketch.

Is the OBD adapter UART or I2C?

If its UART you should use ...COBD obd;....
If its I2C you should not connect it to RX , TX

and i think that the Serial.begin (38400); not need it