All setups are different, if the turntable has a magnetic cartridge you cannot connect it directly to your soundcard - the turntable will require a pre-amp. Some cheaper turntables have this built in to them to allow them to connect to more modern amps with no phono equalisation. If the hi-fi system has a line out facility on the rear of the amp, then you need (probably) dual RCA/phono plugs to a 3.5mm stereo plug lead of suitable length to connect to the line in on your sound card.
Enable the input to your soundcard within the volume control properties, check for level - then RTFM for your audio software
