Download Audacity from here. http://audacity.sourceforge.net/
Connect your line out from the r2r and into the line input of your sound card.
Audacity is free and a very good program to use, you can save in wave or mp3 format.
It will also allow you to edit the tracks, so if say you record a full album in one hit, you can split it into individual tracks if you wish.
If you have RCA outputs on your r2r you can get an adaptor to 3.5mm required for the sound card. You should be able to feed direct from your r2r without need for the amp, try it and see.
If you get stuck come back.
PS nearly forgot, find the settings in Audacity to playback during recording, I can't remember exactly where they are now I havn't played with it for a few years, but you will know what is needed when you see it. Go through all the options and preferences.