You will need a micro USB cable in order to update Magerit METRO. You also have to download this .zip:
Uncompress it to your Desktop. The uncompressed folder must be named METRO (in uppercases). DO NOT RENAME IT!
Connect the module to the computer via the micro USB cable. You also need to connect your METRO to your Eurorack (turn it on). Follow all the steps found in the .txt files in the uncompressed folder. You will see that it is quite simple and fast to update the Magerit METRO!
Here, there is a video explaining the update procedure on both Windows and MacOs systems