(YOU NEED WIN RAR FOR THIS) I'm not sure if its the same as what i done but if its in a folder called "ur mods name" and in there a folder called maps then in there is all the files right click the folder and send to archive, after click the rar option and change the file extension to .iwd (should say "modname.iwd".
After make a folder in ur "call of duty modern warfare 2" directory calleds "mods" and in there make a folder called "ur mods name" and copy into that folder.
if that doesnt work try a tutorial.