Main map Feature: mapsforge
Typically you will download mapsforge compliant maps from openandromaps. But you can create these maps also with the software from the mapsforge library.
A mapsforge map is a “.map” file. This file has to be placed in the directory “MGMapViewer/maps/mapsforge/”
Here is an example of such a map:
As shown already in the Getting Started you can use the mechanisms via
+ 
to download the map you want.