1. Extract the zip/rar file into;

Club Kits go here:

My Documents/Sports Interactive/Football Manager 2008/Graphics/Pictures/Kits/Clubs

You may need to create the folders above, if they do not exist.

International Kits go here:

My Documents/Sports Interactive/Football Manager 2008/Graphics/Pictures/Kits/Nations

Default Kits go here:

My Documents/Sports Interactive/Football Manager 2008/Graphics/Pictures/Kits/Default

2. You may need create the above folders, if they do not exist.