If you want to see the files you need to do so in the explorer window OUTSIDE of FS.
You will not see a single .bgl file within the FS Scenery Library. You dont ADD individual bgl files, you add the folder that FS will look to when loading the bgl files.
If you installed to the default location,
C:\Program Files (x86)\Microsoft Games\Microsoft Flight Simulator X
(Note: Link may only work on Internet Explorer if at all)
then in the MSFX main folder, you need to open ADDON SCENERY folder and look in there. By default, no items will be in that folder. Anything there is what you or the installer added.
As for the files associated with AG, I do not know where they are installed to, but am assuming they are sent to the ADDON scenery folder. If that is the case, you simply need to activate it within FSX Scenery Library. Add the area, navigate to the folder, you wont see any files, click in the middle of the folder window (FSX has a weird glitch with this) to finalize it. Select ok, and it should be active in FS.
If after trying the above it doesnt work or you can not find the files in the EXPLORER, then make a comment here and we will help you find out what is going on. There are enough brains here to change a light-bulb, and thats a physical task. Almost every piece of software available through this forum is created and maintained by currently active members. So you are in a good place.