1. Right-click on the file you have downloaded and select Extract All from the list that appears. 
2. Select a suitable location and make sure the 'Show extracted files when complete' box is ticked.
3. Click the Extract button and when the extracted contents of the zip file appear, copy the aircraft folder into your X-Plane 12 aircraft folder.
4. Launch X-Plane 12 and start a flight using the aircraft.
5. An activation window will appear, prompting you to enter your serial number. Paste the serial number found in Your Account and click the Activate button.
6. After a short pause, a message will appear informing you that the product has been successfully activated. 
7. From the top menu bar, select Developer > Reload Current Aircraft and Art
8. The aircraft is now ready to fly.