Hi, hope this link can help :
In addition to that, I have noticed that when placing airports in X-plane 11/custom scenery, it can be sometimes useful to rename the airport folder with the prefix "airport_", or anything you like provided that it places your airport folder before the global scenery folder (in the alphabetic order).
If all items are well named and organised in the custom scenery folder, to respect the following order :
You can then delete X-plane 11/custom scenery/scenery_packs.ini instead of editing it.
Restart X-plane, it should work.
PS : always read the included instructions when you download a scenery package. Some require additional libraries and sometimes plugins.