Next, click on the New Layer button at the bottom of the Layers & Channels dialog. For the Layer Fill Type, select White.

This should replace your image with a blank white canvas.

Using the Text tool, click on the white canvas and type in some witty text. For this example, I used 125 pixel text; I wanted it to be nice and big.

Finally, use Image > Colors > Invert on your black text on the white background.