By now you know this repository is crap. This is what worked for me on a 1.54 e-ink display. It should work on other sizes as well.
NOTE: This display requires 3.3 data lines. It works on 5v data lines, but just barely. The display is not crisp. I've read it's possible to use a 10k/4k7 resistor divider for 5v data lines, but it didn't work for me.
Download this library
https://github.com/ZinggJM/GxEPD
From Arduino IDE, open the example
Select this display
#include <GxGDEH0154D67/GxGDEH0154D67.h> // 1.54" b/w
Use these pins
GxIO_Class io(SPI, /CS=/ 10, /DC=/ 9, /RST=/ 8);
GxEPD_Class display(io, /RST=/ 8, /BUSY=/ 7);
Connect as follows (display / arduino):
VCC / VCC
GND / GND
D/C / D9
SDI / D11
CS / D10
CLK / D13
BUSY / D7