If you have ARINC424 airport data available in the Aviator Catalog Manager, you can define a site using an airport in that data.
The site properties window uses the Aviator Catalog Interface to display and interact with the available data.
Click on an airport in the list to select it. Click Primary Runway to view the primary runway for the selected airport. You can edit the primary runway properties in the same way that a standard Runway site is defined.