Standard Firmata not loading on Arduino

Error message below::
Thanks guys ,could you pls help to solve this ? urgent .

Arduino: 1.7.11 (Windows 8.1), Board: “Arduino Uno”

In file included from C:\Users\Christine\Desktop\Arduino\libraries\Firmata\utility\SerialFirmata.cpp:20:0:

C:\Users\Christine\Desktop\Arduino\libraries\Firmata\utility\SerialFirmata.h:30:28: fatal error: SoftwareSerial.h: No such file or directory

#include <SoftwareSerial.h>

^

compilation terminated.

Error compiling.

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The SoftwareSerial library should be included with the Arduino IDE so that's strange but I don't have any experience with the arduino.org IDE you're using. Please try updating to the latest arduino.cc version from: http://www.arduino.cc/en/Main/Software

Version 1.7.x was produced by Arduino.org when there were two companies fighting over the Arduino trademark. You should install the 1.8.x version (see the Download tab at the top of the page) and try again.