problems using library with v-0018

Hi, I'm a complete newcomer to arduino, so please be patient if this question seems really basic. I've been trying to use libraries,and I can't seem to get anywhere with them. I should be unzipping libraries into a "libraries" folder, in the sketchbook directory. This is where I have my problem: there isn't a "libraries" folder in that location, and I can't seem to create one in the sketchbook directory. I've tried everything, but I can't seem to make a "libraries" folder in the sketchbook that will work when I hit "import library"in Sketch. I'm running arduino-0018, on a Macbook Pro OS X, v 10.5. ANY suggestions that anyone feels like offering would be greatly appreciated. Thanks! - Banks616