Extract the .zip file, then copy/paste or drag-n-drop the folder that contains the "scenery" and "texture" folders into your FSX/addon scenery folder, then activate it like any other scenery:

1. Start FSX
2. Go to the "Settings" on the User Interface, and select the "Scenery Library" button.
3. Select the "Add Area" button.
4. Double click the "Addon Scenery" folder.
5. Scroll down untill you find the new folder you just added to the FSX/Addon Scenery folder, and double click it.  You should see "scenery" and "texture" folders.
6.Click "Okay"  If you are using Win 7, click on the empty area below those two folders (it's a Win 7 quirk).
7. Then click the "Okay" on the "scenery library" page, and the scenery will be loaded.