There is a group of layer buttons in the map window, labeled "Base", "1", "2", and "3". I downloaded a complete set of ingame maps, but they do not show up unless the "1" button is depressed. The default ingame maps show up when "Base" is depressed. You can have both your downloaded maps and the default maps drawn on top of each just by having multiple buttons depressed. I guess you could even switch to an unused layer, make a label at the spot you are at, and save. Then switch in your custom labels on the map you are viewing by activating the layer you made them on. I haven't tried that yet. But I thought maybe the layer button thing might be why you aren't seeing your downloaded maps, since that confused me for a bit after I downloaded mine.