The reader has a "serial out" jack on the top of it that is supposed to be used to connect it to a computer serial port so that you can display the text on a computer monitor without having to use the LCD display. I know it does not have a video output. The literature that came with the reader says it can be used with a CW terminal program. I am trying to figure out what program would be a good one to use before calling MFJ and asking them, if they even know.
Windows 98 to XP (maybe Vista): Hyperterminal
Vista, Windows 7, Linux, MacOS: PuTTY. http://www.chiark.greenend.org.uk/~sgtatham/putty/
As others have pointed out, you'll need a USB to serial adapter and a custom cable. The instructions that come with the 461 tell you how to make one. It's a fairly simple project, even for someone who's never picked up a soldering iron before.
However, there are better options out there. I never had much luck with the MFJ-461 unless you have a lot of filtering, a 599+ signal, and the sender has an iron fist (or keyboard). Even then it makes a lot of mistakes. I have a program on my Android phone called simply "Morse Decoder" that runs circles around the MFJ box, even with fades and QRM. It also has a much wider frequency band it can hear, so you can dial up the tone that works for your ear instead of what works well for the 461. It won't decode to a PC though. Just putting the phone's microphone next to the radio speaker works well enough, but building an audio interface will improve accuracy.
You can also use a computer program like FLDIGI to receive code. Like the Android app, it will receive over a wide frequency range and does a better job than the MFJ unit. It's also free. Just run the audio output from your radio into the audio input if all you want to do is monitor.
I'm trying not to knock the MFJ unit, but because it doesn't maintain a WPM lock on the received signal it just has a hard time decoding less than perfect audio. One thing it did was force me to improve my antennas and learn how to really use the RF gain knob and the CW settings on my radio. A few years ago I thought what little it could do was magic, but technology marches on.