After completing the installation of GIMP, the first thing you will do is to open a new page or a new blank image. There are several options to do that. You can choose form one of the predefined Templates. Or you can specify the image size by entering the width and height manually. You can choose the measurements in pixels, millimeters, points or picas. The default is pixels.
If you click on the Advanced Options + sign, you will see a drop down box where you can specify the x and y resolution of the image. Default is 72 pixels per inch. There is an option called Color space. it has two choices, RGB color and Grayscale. Default is RGB color.
Under the Fill with option you can choose between Foreground color, Background color, white and transperancy. Default is Background color. In the toolbox you can select the foreground and the background color manually. Default is black and white.
In the comments box you can type your name, a brief description about the image. This information will be stored and will be available in the image properties when you save the image in a specific format and use it. that will help you to identify your image at a later time.