findobject getcomponent

     GameObject.Find("Name of the object you want to access").GetComponent<Name of the Component (Transform,Script,RigidBody,etc..)();
     
     An Example (easy to understand):
     
     GameObject Player = GameObject.Find("Player");
     PlayerController PlayerControllerScript = Player.GetComponent<PlayerController>();
     PlayerControllerScript.run = true;
     
     Another Example:
     
     GameObject.Find("Player").GetComponent<PlayerController>().run = true;

rb = GetComponent<Rigidbody>();