How do I use Singleton Design pattern in unity3d C#

[70140-singleton.zip|70140]

I am try to access scoremanager script by using singleton patterns from game script. The problem I am having game script wont allow to access the script because the error is saying error CS0246 scoreManager . I thought coded the scripts right. I also made the scripts public and I still get the same error. I want to access the scripts in Singleton pattern design. I have both of the scripts in the singleton zip file. Help would be appreciated.

A singleton design pattern in Unity looks something like this:

public class GameManagerSingleton : MonoBehaviour
{
    public static GameManagerSingleton instance = null;

    public int score = 0;

    void Awake()
    {
        if (instance != null && instance != this)
            Destroy(gameObject);    // Ensures that there aren't multiple Singletons

        instance = this;
    }
}


public class ScoreObject
{
    void IncreaseScore()
    {

        GameManagerSingleton.instance.score += pointsEarned;
    }
}

You can access the ‘instance’ variable by qualifying it with the class name. Wherever you type GameManagerSingleton.instance, you’ll have full access to all public fields.

The thing to keep in mind is that everything that you use from an instance variable will ONLY happen from one area, and unless you specifically say, it will be destroyed when the scene switches.

How do I keep the Score text included ?