How to define Frist Start-up (Launch) in script?

So i basically wanted to create tutorial of how to contol the game… but i want it to be shown only at first start-up… Can someone define this in script? It would be helpful for me. Thanks

class Tutorial
{
public bool isFirstStart { get; set; }

      void Start()
     {
            if (PlayerPrefs.HasKey("isFirstStart"){
                 isFirstStart = PlayerPrefs.GetKey("isFIrstStart");
            }
      }

     void TutorialDone()
     {
           PlayerPrefs.SaveKey("isFirstStart", isFirstStart();
      }
}

Something along those lines should help. A simple saved value can help with that. Of course, you can also save it to a file, PlayerPrefs saves to the registry by default on Windows.