1. Create a new document, 800 x 600. Make sure the background is white and create a new layer (Ctrl + Shft + N)
2. Fill this layer with black and go to Filter > Noise > Add Noise.
The settings: Amount – 100, Distribution – Gaussian, Monochromatic ticked.
Okay, first off, create a new document, whatever size you choose. Just make sure that is is slightly bigger than the text you are writing, so that the icicles can fit. Note: the mode must be grayscale!