Open Elektron Transfer and click on "Go to the SYSEX TRANSFER page"

On the next screen, click the "Browse" button and load the OS file, or if your device is not booting and you need to perform an update from the startup menu, click on "OS upgrade via device startup menu" instead.

When you load an OS file, the instructions will change to match the OS file.

If you selected "OS upgrade via device startup menu", you will be taken to the screen below. Click the "Browse" button to load the OS file and follow the instructions.

When you are performing an OS update from the startup menu, you must use a physical MIDI interface connected to the physical MIDI port of your device. It cannot be updated via the USB port from the startup menu.