By selecting this you should be prompted to load a map file.
The standard file extension for Magus Map Maker is *.lvl
After
reading the number of layers is will store the data correspondingly
1 layer - Stores everything
into the middle layer
2 layers – Stored data in the bottom and middle layers
3 layers – Stores data in all three, bottom, middle, and top
layers
To learn the file structure of a map view File_Structure.