To flash the firmware onto the microcontroller, run `make avrdude`, and press the reset button.
make handwired/atreus50:default:avrdude
See the [build environment setup](https://docs.qmk.fm/#/getting_started_build_tools) and the [make instructions](https://docs.qmk.fm/#/getting_started_make_guide) for more information. Brand new to QMK? Start with our [Complete Newbs Guide](https://docs.qmk.fm/#/newbs).