Your KH1 must be connected to a personal computer serial port or USB port before firmware can be sent.
A KXUSB interface cable for USB plugs into a USB port on your personal computer. Insert the 3.5 mm plug into your KH1's Key/Data jack.
A KXSER RS-232 interface cable plugs into a 9-pin RS-232 serial port or a USB to Serial adapter, such as the Elecraft KUSB USB to Serial Adapter. Insert the 3.5 mm plug into your KH1's Key/Data jack.