The manual is here:http://www.mfjenterprises.com/pdffiles/MFJ-464.pdf
. . . Connect the radio's AF (headphone) output to the MFJ "Radio In" jack (for the "code reader" function to work)
. . . Plug a paddle into the MFJ "Key Input" jack;
. . . Depending on your computer, you'll either have a serial port, or you'll buy a USB-to-serial adapter (and if you're
. . . using Windows 7, it should have an FTDI chip, not a Prolific chip):
. . . Make or buy (from MFJ) a DB-9-to-stereo-plug cable, and connect it between the
. . . MFJ "serial" jack and the computer's serial port;
. . . Connect the MFJ "Keying Output" jack to the rig's "Key" jack, and _turn off the rig's internal keyer_.
That should get you started.
It can take some fiddling to get the computer-to-rig connection working right.
. . . what software will you be using ?