To use the display, you will need to install the Adafruit_EPD library (code on our github repository). It is available from the Arduino library manager so we recommend using that.
From the IDE open up the library manager...
And type in adafruit EPD to locate the library. Click Install
If you would like to draw bitmaps, do the same with adafruit ImageReader, click Install
Do the same to install the latest adafruit GFX library, click Install
If using an earlier version of the Arduino IDE (pre-1.8.10), locate and install Adafruit_BusIO (newer versions handle this prerequisite automatically).