4. Fill with color
Next you’ll have to fill the new layer with black. Select the Paint Bucket tool from the Toolbox, set the Primary Color to black in the Colors window and click anywhere in the new layer. To bring up the Colors window, press F8. To bring up the toolbox, press F5.
5. Add noise
You might not believe it, but the magic begins with a little noise. Go to Menu < Effects < Noise < Add Noise. In the Options window that pops up, set the Intensity to 100, the Saturation to 0 and the Coverage to 30 as in the image below.