As MHOOKEM said, you will need some software. I use Calkwalk Pyro to record my old vinyl to disk, but there are many programs out there.
Be advised that you almost certainly will need an attenuator to do this, as the input will be to high, causing volume control and noise problems. Before you lose any sleep about getting an attenuator, just go down to Radio Shack and get a volume control for Walkmen headphones. It has the same mini plugs, so you can just connect it in series and turn it down until the input to the PC is satisfactory. Then you never touch it again.