However, the QMK Toolbox is only available for Windows and macOS currently. If you're using Linux (or just wish to flash the firmware from the command line), proceed down to [Flash Your Keyboard From The Command Line](#flash-your-keyboard-from-the-command-line).
Begin by opening the QMK Toolbox application. You'll want to locate the firmware file in Finder or Explorer. Your keyboard firmware may be in one of two formats- `.hex` or `.bin`. QMK tries to copy the appropriate one for your keyboard into the root `qmk_firmware` directory.
Once you have located your firmware file drag it into the "Local file" box in QMK Toolbox, or click "Open" and navigate to where your firmware file is stored.
In order to flash your custom firmware you have to put your keyboard into a special flashing mode. While it is in this mode you will not be able to type or otherwise use your keyboard. It is very important that you do not unplug your keyboard or otherwise interrupt the flashing process while the firmware is being written.
Different keyboards have different ways to enter this special mode. If your PCB currently runs QMK or TMK and you have not been given specific instructions try the following, in order:
* Hold down both shift keys and press `Pause`
* Hold down both shift keys and press `B`
* Unplug your keyboard, hold down the Spacebar and `B` at the same time, plug in your keyboard and wait a second before releasing the keys
* Press the physical `RESET` button on the bottom of the PCB
* Locate header pins on the PCB labeled `BOOT0` or `RESET`, short those together while plugging your PCB in
When you are successful you will see a message similar to this in QMK Toolbox:
This has been made pretty simple compared to what it used to be. When you are ready to compile and flash your firmware, open up your terminal window and run the flash command:
This will check the keyboard's configuration, and then attempt to flash it based on the specified bootloader. This means that you don't need to know which bootloader that your keyboard uses. Just run the command, and let the command do the heavy lifting.
However, this does rely on the bootloader being set by the keyboard. If this information is not configured, or you're using a board that doesn't have a supported target to flash it, you will see this error:
WARNING: This board's bootloader is not specified or is not supported by the ":flash" target at this time.
Give it a try and make sure everything works the way you want it to. We've written [Testing and Debugging](newbs_testing_debugging.md) to round out this guide, so head over there to learn about validating your firmware and how to troubleshoot your custom functionality.