if u want the skin for Allied Assault put it in the mohaa/main file if you want to use it for Spearhead put it in the mohaa/mainta file...if this doesnt work seek guidance
Make sure that the PK3 file is in the mohaa/main sometime skins are packaged in folders and when you extract them it extracts the folder so i you might have to go in the folder and cut the pk3 then paste in the mohaa/main .. Hope that helps