Arasina, simply patch one end of the cable (male mini-jacks at both ends) into the LINE IN input on the sound card, patch the OTHER end into the OUTPUT on your source player.(headphone output will do)
It may be a good idea to start with the volume really soft...do some test recordings to hear the proper level that can be done without distortion. After all, ya don't wanna blow out your sound card; speaking from personal experience here. ;>)
And the LINE IN input on the sound card is where, exactly? :o)