The board reset into bootloader mode via either the reset button (on the back of the PCB) or a configured `QK_BOOT` shortcut (which may vary depending on when the PCB was flashed).
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).