This is the Prusa Firmware for Prusa i3 Mk2, modified to work with generic RAMPS hardware (or, better yet, a board with more mosfet outputs like MKS BASE or MKS GEN).
Configuration_prusa.h is already there, you don't need, or want, to copy a config from the variants directory.
Ideally, your board has a MOSFET on D7, and you should connect the extruder cooling fan to that (NOT the part fan). The firmware is setup for Dual Z steppers using the E1 driver. It won't matter if you use the Z driver for both either in series or parallel either.
Good luck!!!
Install arduino
Remove Liquid Crystal library from your arduino or rename it (not certain this is really necessary anymore)
Install the arduino addon located in the root of this repo. Don't forget to install correct version! (not certain this is really necessary anymore
Upload the firmware to board