“script” should be the exact name of your script. I assumed you were just using that name as an example. So for example if I create a script called “PlayerHealth”, I would reference it like this:
public PlayerHealth playerScript;
void Start ()
{
playerScript = playerScript.GetComponent<PlayerHealth>();
}
It says “script cannot be found” because it doesn’t actually exist. Hope that helps, if you have any other questions let me know.