Windows Media Player/Realtek 97 Sound card

I just wired my stereo into the in line on my sound card because I want to play cassettes on the stereo and convert them to discs on my computer. The wiring is all external, so I am in the sound card with a normal plug. I cannot find any way to convert the in line from the sound card to play through or add to my library in Windows media player. I also have Real player installed on my system, but have not used it as yet. Also there is a radio station I like on the Internet, and I can play it through Windows media player, but am unable to record any of the music. Can anybody tell me what I am doing wrong? I have a CD-Rom, and DVD-RW on my system. Appreciate your help, John.