Ok , I was a bit confused at first too but I soon got the hang of it.
Have you downloaded the graphics? Yes?
Well if they are a rar. file then you will need to extract them using WinRar which can be downloaded for free (demo)
Then once extracted you should have your files.
Go to your user documents, and find Sports Interactive
You should be in something like this
C
Documents and Settings\user\My Documents
Go to "Graphics" and in that folder create two new folders "Players" and "Kits" , move the files you have just extracted with WinRar , into the destined folder , for eg.
Premier League 07/08 Facepacks - Players
Premier League 07/08 Kits - Kits
Hope it helps,
Kev