Using Masks and Layers—Painting, Filling, and Color Tools - GIMP 2.6 for Photographers: Image Editing with Open Source Software - page 220

You have now learned several important methods for “freshening up”
a sky in an image. You learned how to handle a number of complex tools.
Perhaps you're so proud of your beautiful picture that you want to create a
greeting card with it. All you need now is to learn how to use the Text tool so
you can add some words.
Figure 3.45
The window of the Supernova filter. With a click in the preview window, you can determine the approximate position of the generated
light reflection in the picture. If you apply the effect at an individual level, you can subsequently position it more precisely with the
Move tool.