Recording audio from an external source,radio or audio cassette tape

I'm using Audition 1.5. With Windows 7. I'm trying to record audio from an audio cassette tape. I'm using line in and the sound is going to the computer speakers, but it will not record. I can import audio files into Audition and they will show a wave form and play. I have tried to use the Amplitude/Play effect. When I open the effects tab expand Amplitude and click on  Amplitude/Fade, nothing happens. That tab is greyed out. Can you help me?

Dick Brown

jrbrown55@sbcglobal.net

309/691-0606