Instructions
Close the "Microsoft Flight Simulator 9" game.
Open your Web browser and navigate to the website that hosts the scenery add-on that you want to install.
Download the scenery add-on file to your hard drive. Add-on files are usually packaged in compressed EXE or ZIP format.
Double-click the file that you downloaded. If the file is a self-extracting EXE, then click "Browse" and navigate to a temporary folder that you will extract the files to. If you downloaded a ZIP file, then click "Extract All" and browse to the temporary extraction folder.
Open a Windows Explorer window and navigate to the temporary extraction folder that you created. Locate the folder that contains both "Scenery" and "Texture" subfolders.
Right-click the folder that houses those subfolders and click "Copy" in the menu.
Navigate to the "C:\Program Files\Microsoft Games\Flight Simulator 9" folder using the menu tree on the left side of the Explorer window.
Right-click the "Addon Scenery" folder and click "Paste" in the menu. Your add-on scenery is installed and ready for use with "Flight Simulator 9."