Ok:
Skins go in:
C

Documents and Settings\Owner\My Documents\Sports Interactive\Football Manager 2007\skins
Pictures/logos go in:
C

Documents and Settings\Owner\My Documents\Sports Interactive\Football Manager 2007\graphics\pictures
Run FM2007 and go into preferences and turn off the skin cache. Then go into the drop down list of skins and you should see a list of your newly installed skins.
Choose 1 and click "Confirm". Afte the new skin has loaded up select Skin Cache and then "Confirm" again and you should see all your new pictures/logos.
Under the:
C

Documents and Settings\Owner\My Documents\Sports Interactive\Football Manager 2007\Graphics\pictures
You should have further folders like:
logos
kits
players
backgrounds
Depending on what you have downloaded.
Follow the setup of your install directory to see the structure:
C

Program Files\Sports Interactive\Football Manager 2007\data\graphics\pictures