As I've said, the most important thing to start diagnose any problem, is to known if you see the Addon Manager menu under the Addons menu in FSX. If not, that's an entirely different course of action, and it's explained in the Troubleshooting section of the manual.
If yes, you have to check if you see fsdreamteam listed under the Publishers list in the Addon Manager. If FSDreamTeam is there, and the scenery is present in the Scenery Library, then you have to check if you have these files:
c:\ProgramData\Esellerate\Esellerateengine.dll - if you are running Vista OR
c:\Windows\Esellerateengine.dll - if you are running XP
If you see this file, than it's all fine, and you SHOULD see the scenery! If you are missing some files, please reinstall and, expecially under Vista, be sure to have administrator rights to the machine.