The way i did it for my collection :)

1) Get a two-side RCA jack cable ( fancy name for the stereo cable connectors we're all used to ). Connect one end to the "Line Out" / "Out" of your stereo/hi-fi ( tenj :) and plugin the other end into the "Line In" of your PC

2) On your PC, start Audacity and click on "Record" and change the source to "Line In" or "Stereo Mix". Play the tape on your tenj *at relatively low volume* and watch the Audacity waveforms to see if you're getting any input. You can do several trial runs to ensure you're getting in the music ok and that your volume settings are ok . [ Stop the recording on Audacity and playback  then restart (as many times as necessary) ]. When satisfied that the setup is ok, start Recording on Audacity play the tape from the start.
[ *Emphasis on low volume because the higher the volume, the higher the *noise* (electronic & otherwise). Volume/loudness can be fixed later ( see below ) ]

3) When you're done recording, select the tracks as desired & "save selection" to WAV/MP3 ( MP3 is preferred :) You can also save the whole track ( if you want it like that ).

4) By this stage, you have several MP3's / one *large* MP3 of your favourite tape music. Next step is to enhance the decibels :) For this, MP3Gain will sort you out just fine :)

5) You can still re-open the MP3 file or raw recorded files with Audacity and apply DSP effects to your music. For example, bass boost, noise removal, cross-fade, and so on

Happy recording! :)