Code Error

I purchased a RFID reader and I pulled a servo out of an old RC plane. the goal is to use the servo to lock and unlock my dorm room door with just a tag. i was able to find a code but the writer make an error in the line that states:

“SoftwareSerial RFID = SoftwareSerial(rxPin,txPin);”

the error reads:
" In function ‘void loop()’:
error: ‘SoftwareSerial’ was not declared in this scope"

i have no clue how to declare it.
any help?

#include <SoftwareSerial.h>
http://www.arduino.cc/en/Reference/SoftwareSerial