Follow this procedure to manually activate Vidan Design add-on scenery in P3D (with Billund X as example):
1. Make sure that P3D is not running
2. Run the installer and follow the instructions
3. Run P3D and load any flight
4. On the menu bar, go to World > Scenery Library:
5. In the Scenery Library, click on the "Add Area" button:
6. In the Add Scenery Area window, click on the "Browse" button:
7. Browse to the "Billund X" folder and highlight it (click on it only once). The Billund X folder is located in the main P3D folder under "Vidan Design". Next, click "OK"
8. In the Add Scenery Area window, click "OK":
9. Billund X has now been added to the Scenery Library. Click "OK":