Just go over to http://wwwflightsim.com
, and if you haven't done so already, Register - they've got a file library with add-on scenery for just about every airport imaginable - download the one you want and install.
If there's more than one add-on available for the airport you want it can take a bit of experimentation to find one that you like.
It's not AFCAD files you want though, they only add taxiways etc - the files you want are specifically "Scenery" files. You'll know you've got the right ones when you d/load them as the .zip file will contain one or more files with a ".bgl" extension.
Statistically, people who have had the most birthdays tend to live the longest.