Merlin:

In order to get the wave files into the computer, you will first have to hook up a cassette player's output, to the input of the soundcard on your computer. Then play the cassette tape while recording the output into a computer program (like RealBand or Audacity).

Then open BIAB and (as Charlie indicated above) use File > "Open audio with chords". That will open BIAB Audio Chord Wizard and go from there.

If this info is too general, give us more specifics on your cassette setup and someone will be able to help you.

Good luck!
LLOYD S