Have you put them in the correct folders?
If so go into preferences>display and sound then unclick use skin cache and click always reload skin on confirm and this will sort you out.
Please search before creating a new thread as this question has been asked several times.
Did you put the downloaded files in the correct place?
C:\Documents and Settings\Administrator\My Documents\Sports Interactive\Football Manager 2011
Can you be more specific to what files you have downloaded and which ones u want to use?
Skin in skins folder and MU data Update in editor data folder. Then do what Steve said.So far I downloaded a skin and the MU data Update under the transfer updates section. I placed both of them in files inside the Football Manager file but I cant seem to find either when I play the game.