I'm in a bit of a big problem. I have bought today Las Vegas. For some reason, I can't find my scenery in the FSX Library so I can't see the scenery..
The installer automatically adds the scenery to the Scenery Library, unless you have an error in your scenery.cfg. But if you have an error in your scenery.cfg, you should have seen an error during the installation. Have you see any errors while installing ?
If you haven't seen any errors, a possible cause of the problem is that you are running FSX in "Compatibility" mode, like XP under Windows 7/8, etc. This is not how FSX it's installed by default, and it will also cause performance problems, and it will change the location of some folders using by FSX, including the location of the scenery.cfg
So, check in the file Properties/Compatibility for FSX.EXE, that NOTHING is enabled in that page. No Compatibility mode should be checked.