See [build environment setup](https://docs.qmk.fm/#/getting_started_build_tools) then the [make instructions](https://docs.qmk.fm/#/getting_started_make_guide) for more information.
Because the two boards are identical, the firmware has logic to differentiate the left and right board. It uses two strategies to figure things out, [EE_HANDS](https://docs.qmk.fm/#/feature_split_keyboard?id=handedness-by-eeprom) or [by define](https://docs.qmk.fm/#/feature_split_keyboard?id=handedness-by-define). See [setting-handedness](https://docs.qmk.fm/#/config_options?id=setting-handedness) for more information.