Insert the black and white jacks into the "Line Out" sockets on the back of your tape deck. Plug the other end--the mini-jack--into the "Line In" on the back of your computer or the headphone socket if you are using a laptop.
Open your audio-editing program and set the program to record a new track.
Make sure the "Line-In" option is selected on the program, then press "Play" on your cassette deck. Adjust the volume so that it does not exceed the maximum recording level on the software.
Press "Stop" once the levels are set. Rewind your cassette to the beginning.
Click "Record" on your music recording software. Press "Play" on your cassette deck. Save the recorded music to your desktop.