First you need to download XPLANE 9 DEMO from xplane.com not .org. Second, download aircraft and place into XPLANE 9 DEMO, AIRCRAFT folder. Then open the Plane Maker from the XPLANE 9 DEMO and just save the aircraft dont press 'save as'. Move the aircraft into the XPLANE 10 AIRCRAFT folder. Open in the XPLANE 10 Plane Maker and 'save' again. Then open the aircraft FOLDER and there should be a folder that says 'PLUGIN for MAC-LINUX-WIN. Open it up and choose what system you run on and the plugin that supports that OS. For example I run windows so I would use the xpfw757_win.xpl plugin. Finally copy it into the plugins folder,(X-plane 10/Resources/plugins. Hope this helps, if not check out this video: