Additional documentation can be found at the Marlin Home Page.
This version is configured for a stock build of the Mendel90 kit. It has two additional thermistor tables to match the thermistors supplied in the kit.
For a standard kit just these two lines will need tweaking to match your exact E_STEPS_PER_MM
and Z_MAX_POS
as described in the configuration section of the build manual.
To build Marlin 2.0 you'll need Arduino IDE 1.8.8 or newer or PlatformIO. Detailed build and install instructions are posted at: