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
If using an earlier version of the Arduino IDE (prior to 1.8.10), also locate and install Adafruit_BusIO (newer versions will install this dependency automatically).
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