Once you've downloaded it you'll be presented with a ".zip" file.  Extract this file to the following location "My Documents ? Sports  Interactive ? Football Manager 2014 ? graphics". 
If the "graphics" folder doesn't exist you can simply create it. 
If you are asked to overwrite any files it's okay to do so, but if  you're downloading packs in multiple parts make sure to unzip the oldest  packs first otherwise the old versions will overwrite the new ones. 
Once you've done this, load up Football Manager and go to  "Preferences" and then "Display & Sound". Make sure that you tick  the check box on the page called "Always Reload Skin on Confirm" and  un-tick then box saying "Use Skin Cache". Hit Confirm. 
There should be a box that pops up saying "loading image data for  the new skin". Once this is done your graphics should be working within  the game. 
If you want you can know go back into "Preferences" and "Display  & Sound" and un-tick "Always Reload Skin on Confirm" and re-tick  "Use Skin Cache".