That stepper motor needs a specialized stepper motor driver that can limit the current to protect the motor. If you provide 12v to that motor it will try to draw 12/1.6 = 7.5 amps. If that current was available the motor would be destroyed. With a 2 amp power supply the power supply will be seriously overloaded. With a suitable stepper driver your power supply would probably be sufficient.
Unfortunately the cheap stepper motor drivers that are used in many Arduino projects (such as the Sparkfun BigEasydriver) will not have the capacity for your motor. You need a stepper motor driver with a current capability of 4 or 5 amps and they are much more expensive.
Note, also, that the standard Stepper library is not suitable for stepper drivers that take step and direction signals. Use the AccelStepper library or just write your own code.