Instructions
Download
Close the Microsoft Flight Simulator X application.
Download the add-on files to your computer. Your add-on files will be compressed in either a self-extracting EXE file or in a ZIP file.
Double-click the downloaded file. If the file is an EXE file, click "Browse" and specify a temporary folder that you would like to extract the add-on files to. If the file is a ZIP file, click the "Extract all" button and specify a temporary folder for extraction.
Press the Windows logo and R keys to open a run box. Type "explorer" into the box. Press Enter. A Windows Explorer window opens. Use the menu tree on the left side of the Explorer window to open the folder to which you extracted the add-on files.
Open a second Windows Explorer window. Type "c:\Program Files\Microsoft Games\Microsoft Flight Simulator X" into the address bar at the top of the Explorer window and press Enter.
Install
Switch to the first Explorer window and right-click the folder that contains the files for the airplane, gauges, or effects that you wish to add.
Click "Copy" in the menu.
Switch back to the "Microsoft Flight Simulator X" Explorer window and right-click the sub-folder for "Airplanes," "Gauges" or "Effects."
Click "Paste" in the menu. Your new add-on will be available the next time you run FSX.