Open your copy of Photoshop and create a new image from the "File" menu. In the attributes for this file, you should ensure the image file is 300-by-300 pixels, in RGB color mode with a 72 pixels-per-inch resolution.
Navigate to the "Layer" menu, click on "New" and then click on "Layer." Select the paintbrush tool and create a shape or paint a message on the canvas.
Navigate to the "Layer" menu once again. Click on "Effects" and then "Drop Shadow," and click "OK." This will apply this particular effect to the layer created in step three, making an impressive three-dimensional effect.