Once you have the image, launch GIFConverter and open the image. You should see a Mercator map of the world with land masses in black and bodies of water in color or gray scale. The image will also be much larger than the size of your screen. You can reduce the size of the system by restarting your Mac with the shift key held down. This will turn the extensions off.
Image works best if it has as much RAM as it can get.
Four megabytes works fine, more is better. The image will be larger than the screen. You will want to undo this at some point to get a close look at smaller regions. Note that the range of data can be very small. There are several tools in Image that can dramatically increase your ability to interpret the data.