the turntable would have to either be going into an amp or a mixer. then u could get a cable that goes from the back of the mixer (phono out) to the line in or mic of ur laptop (3.5 headphone jack).

or if it were plugged into an amp, its unlikely that u'll have a phono out so u could go from the amps headphone jack straight to ur laptops line in or mic. Either of those wires can be got from ebay for a couple of notes. its pretty ghetto but it'll do ur basic job