What mod are u trying to install? make sure you extract mods "with path" into that folder meaning under mods folder if the mod name is "evil map"(example) then check under mods folder if there is a folder called \evil map\ and make sure under that folder there is mod.info file and other subfolders such as \resource\ or/and localization that contains other subfolders and files. If you find that everything under that evil map folder for example is located without subfolders just bunch of files that means u did not extract the file properly. Further, make sure the mod u trying to install is good and not some test thing.
Let me know what mod you trying to install.
For example if you download my mission battle of montcuit -
http://www.moddb.com/games/men-of-wa...ntcuit-ver-215 and extract it that will work for sure, but it still doesnt show in the game that means either you have mowas installed in another folder or mods folder is not properly named maybe u have it as mod? or you extracted without path meaning battle of montcuit folder was created but nothing under it was properly extracted.
If you still have problems let me know