Download the GS File viewer, which can be found on this website.
http://www.citiesinmotionexchange.com/index.php?/files/category/2-tools/
Install it.
Go to your root folder of Cities in Motion.
Create a folder named ''metro''
Open metro.gs with the GS file viewer.
Select then ''Unpack whole GS file to folder...'' (button in the middle)
Unpack it in the newly made folder ''metro'' in your root folder.
So now you have a folder called ''metro'' and it full of other folders and files.
That's good, you've unpacked metro.gs to the folder metro succesfully.
Rename ''metro.gs'' to ''metro.old.gs''
The game can read a normal folder the same as a .gs file.
Now you can put the files of a mod in the folder ''metro''.
You couldn't do that before because you couldn't open the metro.gs file.
To add a map, just go to your documents and then to the cities in motion folder.
Go to maps and put all files in there.
Niels