ec390 update instructions

1. Check the serial number underneath the machine... (MUST begin with 2022...)
2. Copy the update file (SH05.SAH) onto a blank (FAT32 formatted) USB stick.
3. With the machine powered off, insert the USB stick into the port at the back of the ec390.
4. Power on the machine.
5. Machine will display a progress indicator whilst installing update.
6. Once prompted, turn off the machine, remove the USB stick, and power machine back on.
7. Test for correct operation. Done.
