How to load font into variable

I have .ttf font called Kubasta that put into Assets > font folder. I call it like this, but get an error.

  void OnGUI() {
     GUIStyle myStyle = new GUIStyle();
     myStyle.font = kubasta;
     GUI.Label(new Rect(10,10, 100, 30), "Hello World!", myStyle);
     if (!kubasta) {
         Debug.LogError("No font found, assign one in the inspector.");
         return;
     }
  }

I've tried calling it by it's file name Kubasta.ttf, Kubasta, and kubasta but i get the error, 'Debug.LogError("No font found, assign one in the inspector.");' in it's current context.

What's going on?