In the SAM Content Manager menu you can download and activate AirportVehicles extension. If you bought it on Steam it will be installed and activated automatically.
Check out where you can buy the AirportVehicles extension here.
COMPATIBILITY
X-Plane 11
- Windows 10/11: compatible
- Linux Ubuntu (latest LTS): compatible
- macOS: compatible from 10.14 to 12.1
X-Plane 12
not compatible