You can find our Nokia Display Arduino library on github. You should install it through the Arduino Library Manager.
Open up the Arduino Library Manager:
Search for the Adafruit PCD8544 library and install it
Search for the Adafruit GFX library and install it
We also have a great tutorial on Arduino library installation at:
You should see the pcdtest example in File>Examples>Adafruit PCD8544 Nokia 5110 LCD library. Load that example and flash it to your Arduino