If you have made everything correctly, you can now go into Map-maker, which is located in the 'Tools' section, under the name of Map Maker.
Go into the second tab and write in the name of the Greyscale and the Mask, then viola, your map is there.
Once you've completed everything, click the 'Export' button and you can find all of your maps (and other ones you've downloaded) in Cape of Distant Worlds.