This thread will take you through basic steps in Gimp. It will be updated now and then with more images and tips. The main goal is to draw some simple figures and manipulate them using the layers.
Double click on the Gimp icon. Click on [File], [Open] and browse to your image file opening it (you can find the example file here
). A difference between Gimp and other image editors is that you don't have everything into the same window: you will find three main windows to be managed.
One window contains the image itself, a second window contains the basic instruments to manipulate the image, and a third window contains the layers editor. If you don't see this last window you can load it by [CTRL+L]. Hence you can modify the size of each window following your needs.