Cool Edit's known for *removing* clicks and pops and background noise, not adding it lol. As far as I know, it doesn't have an effect that adds that kind of noise. So there are two options: find a plugin that does that; or record an old vinyl record - just the five seconds before the music starts or the five seconds when the music ends that's got the scratchy sound. Then loop what you've recorded and add it as another track to the mix.