You've decided to use GIF Construction Set. This is a good choice in a program because you don't need to convert images from bitmap format. If you haven't taken the 2D design tutorial, I suggest that you do so since the methods of drawing used in this tutorial are explained there.
Ok, now to the real stuff. To begin making an animated GIF you need to know what you want to animate, and how you want it to move. Let's say you want to animate a circle to make it bounce like a ball. Here is how you need to go about doing this. First you need to open a drawing program.
Once the program is open, set the size of the canvas to 2 by 2 inches. Next draw a circle that's small enough that it can be seen moving when animated (See diagram 1). Save this images in a new folder as circle001.bmp
Diagram 1.
Once a circle like the one above has been drawn, take the select tool and box in the circle. Move the selection of the circle up a bit (See diagram 2). Save this image as circle002.bmp
Diagram 2.
After an image like diagram 2 has been created, select the circle again with the selection tool in Paint Brush. Move the circle down just past the original position (See diagram 3). Save this image as circle003.bmp
Diagram 3.
Now you are ready to animate the circle.