Yep, basically you will need to modify the following as Artik says in config.ini (I usually open it in Notepad):
# Map size in miles
# -----------------
#
# Valid values are 64, 128, 256 and 512
#
map_size=512
I have mine set to 512 which generates as 512 mile by 512 mile map.
Then look for:
# Map Region
# ----------
# you need, specify latitude and logitude of central
# point and the map scale
Under this you want to put the coordinates for your maps:
# Battle of Britain
#lat=50.52
#lon=-0.28
#scale=1.0
#Israel Area
lat=31.25
lon=33.77
scale=1.0
Note that the # tells the program to not read this line. So you can save multiple coorindates here like I did above BUT there can only be one non # lat, lon, and scale.
The lat and lon tell the center point on the globe that it will create your map from. The scale tells the program what the relationship between the game map is and the real world. scale=1.0 is 1 game map mile equals 1 real world mile. If you had the scale at 1.5 it would be 1 game map mile equals 1.5 real world miles.
I usually use
http://earthexplorer.usgs.gov/ to get the lat and long I want to create my maps. I will get the rough coordinate, set my scale, and then run the program. First time might take a little bit of time because it fetching actual dem files. After that when you tweak by adjusting scale or shifting the lat and lon a little bit it is faster. Best way to check things is to run the program and then go look a the clipboard map it generates to see if it is covering the area you want. It will be in your output directory and the file name is mymap.bmp.