Instructions
Open a Web browser and navigate to FSDeveloper.com. Click the "View the downloads..." link to view the available FSX downloads.
Click the "Scenery Design" link, followed by the "Tools" link to view the scenery placement and design tools for FSX.
Click the link that corresponds to the scenery tool that you want to download. Click the "Download" link to download its ZIP file.
Double-click the ZIP file to extract its contents. Double-click the extracted folder to view its contents. Double-click the EXE file and follow the onscreen instructions to install the scenery tool.