Question AR Foundation Errors No Active...

Hi! I've been using Unity for the past 6 months, and now my project requires to use AR.
I'm really new at AR, and there's somethings I don't quite understand. Current setup is on a Macbook.
Installed AR Foundation and ARKit for iOS.
I can't start working, because there's 4 warnings that I can't and don't know how to get rid off. I've searched, and can't fix this.

1) Warn Unity No active UnityEngine.XR.ARSubsystems.XRSessionSubsystem is available. Please ensure that a valid loader configuration exists in the XR project settings.

2) No active UnityEngine.XR.ARSubsystems.XRSessionSubsystem is available. Please ensure that a valid loader configuration exists in the XR project settings.
UnityEngine.XR.ARFoundation.ARSession:OnEnable ()

3) No active UnityEngine.XR.XRInputSubsystem is available. Please ensure that a valid loader configuration exists in the XR project settings.
UnityEngine.XR.ARFoundation.ARInputManager:OnEnable ()

4) No active UnityEngine.XR.ARSubsystems.XRCameraSubsystem is available. Please ensure that a valid loader configuration exists in the XR project settings.
UnityEngine.XR.ARFoundation.SubsystemLifecycleManager`3<UnityEngine.XR.ARSubsystems.XRCameraSubsystem, UnityEngine.XR.ARSubsystems.XRCameraSubsystemDescriptor, UnityEngine.XR.ARSubsystems.XRCameraSubsystem/Provider>:OnEnable ()

 

Please enable the ARKit provider in the 'XR Plug-in Management' window.

 

[{
"resource": "/C:/Users/This PC/Almost Real app/Assets/InputManager.cs",
"owner": "csharp",
"code": "CS0234",
"severity": 8,
"message": "The type or namespace name 'ARFoundation' does not exist in the namespace 'UnityEngine.XR' (are you missing an assembly reference?) [Assembly-CSharp]",
"source": "csharp",
"startLineNumber": 4,
"startColumn": 22,
"endLineNumber": 4,
"endColumn": 34
}]
i have this error