if you save the map in the program files galaxy folder then depending on the number of players and number of planets & stars it is placed in the deifferent sizes ie small,medium & large in vanilla sins ONLY.
for entrenchment with the map in the program files galaxy folder the map will NOT be seen unless you modify the galaxy.manifest
assuming you have sins 1.17/entrenchment 1.03, the galaxy forge maps NEED to be placed here for xp
C:\Documents and Settings\'user name'\Local Settings\Application Data\Ironclad Games\Sins of a Solar Empire\GalaxyForge
or here for vista/windows 7
C:\Users\'user name'\AppData\Local\Ironclad Games\Sins of a Solar Empire\GalaxyForge.
NOTE the first two folders after the 'user name' are hidden , so to see them you must first click on 'tools' then 'folder options', then 'view', then click on 'show hidden files& folders' then click ok, then you will be able to browse your want to the folder. I suggest when you find the folder that you create a shortcut to it on the desktop
also the galaxy forge maps only show up in the galaxy forge tab of map types
and if a map you want to play was released before 25th feb 2009 then you will also neet the sins map updater from here
http://files.filefront.com/sins+map+updater+v201rar/;13585432;/fileinfo.html
harpo