1. If you want to go through the tutorial, then unpack "AR Football prefabs.zip". If you want to see the final result, then unpack "Finish Assets.zip".
2. Window => Package Manager

Unity Registry

* Multiplayer HLAPI (for Multiplayer)
* AR Foundation (for AR)
* ARCore XR Plugin (for Android)
* ARKit XR Plugin (for IOS)

Built-in Packages

* Android JNI

For Enable complete scripts in Final Assets folder add "ENABLE_AR_TUTORIAL" in Player Settings => Scripting Define Symbols