First you have to download the edited database
. If its a zipped or .rar file you need to unzip it first. Use winzip, Jzip or 7Zip to do that. Jzip.com or 7zip.com and download their freeware program.
Then Place the .dbc or .xml file in this folder.
Documents\Sports Interactive\Football Manager 2012\editor data
If you don't have an editor data folder just go ahead and make one.
Now, some Windows users will have two Sports Interactive Folders. Make sure you use the one that has more folders in it than the other one. For some reason windows makes two folders for the game when installing.
Next start a new game.
You will get a screen similar to this one.
Check the change box for editor data files. This brings up all the edited databases you have in that folder.
Tick the one you want and continue and you are all set.