Removing background, help!

[Random Stranger]

I'm using CS4, and I want to remove the preset white background of the canvas so I can copy it onto a background layer, I know it's possible, but I've forgotten where I find that function, it removes the background preset and the background shows up as a checkerboard thing in dark and light grey, anyone know how I do this?

[Imaginary]

There should be something called "Background contents" in the window that pops up when you click "New" under "File", change it to transparent.