If you want to use Realistic Engine Sounds with NWH Vehicle Physics,
import NWH Vehicle Physics, Realistic Engine Sounds and NWH_RES-Plus.unitypackage.
This unitypackage contain demo scenes, scripts for demo scenes and prefabs for NWH Vehicle Physics.
This prefabs are ready to use with NWH Vehicle Physics.

Get NWH Vehicle Physics here: https://assetstore.unity.com/packages/tools/physics/nwh-vehicle-physics-107332?aid=1101l3r5B

Read the documentation for tutorials.