You'll need a TV Capture Card.
Software like PowerVCR.
Connect the VCR to the TV Card with the RF cable.
Select Antena Mode on TV Card & manual search the channel on which the video is playing.
Select the format of recording (MPEG-1/2, etc.) & click record.
Just did in the same way.
But, I recommend you record a VHS in MPEG-2. Gives far better quality than MPEG-1.