1. go to your mw3/main/iw_06/images [open iw_06 with winrar]
2.download and extract the skin file
3copy the extrated files to the images folder of iw_06
4.go and check the skins in 'create class' in -game,the default camos will be replaced by the custom ones
IMP make sure to back up your iw_06 file,also make sure your game is closed when u do this,one more thing,other players will not be able to see your custom skin ,if they haven't installed it ,but u will be able to see your skins on their specific guns
How many times are you active in the server in a week?
You need to show some activity here. I've seen you sometimes in the server and I've thought that you aren't here as much. So you can consider this as a warning. Stay active or expect the worst.