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
if the map you created was saved in the program files galaxy and you did not edit the entrenchment\galaxy.manifest then that could be another reason that you can not see it.
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