How do i add my objects to a tag

Questions & Answers
1

I’ve made this “frogger” game with 8 cars, but i want to have an “up” and a “down” tag so i dont have to make a startcar1-100 for every car. I already made the tags but i dont know how to add the objects to the tag

using UnityEngine;
using System.Collections;

public class scriptCar : MonoBehaviour {

	public GameObject up, down, startCar1, startCar2, startCar3, startCar4, startCar5, startCar6, startCar7, startCar8;
	public float speed1, speed2, speed3, speed4, speed5, speed6, speed7, speed8;
	public int score;

	// Use this for initialization
	void Start () {

	}
	
	// Update is called once per frame
	void Update () {
		
		speed1 = Random.Range (5, 10);
		speed2 = Random.Range (7, 12);
		speed3 = Random.Range (1, 6);
		speed4 = Random.Range (9, 14);
		speed5 = Random.Range (4, 9);
		speed6 = Random.Range (6, 1);
		speed7 = Random.Range (7, 12);
		speed8 = Random.Range (3, 9);

		startCar1.transform.Translate (0, -speed2 * Time.deltaTime, 0);	
		if (startCar1.transform.position.y < -9){
			startCar1.transform.position = new Vector3 (-2.3F, 8, 0);
			
		}

		startCar2.transform.Translate (0, -speed2 * Time.deltaTime, 0);		
		if (startCar2.transform.position.y < -9){
			startCar2.transform.position = new Vector3 (-1.65F, 8, 0);
		}

		startCar3.transform.Translate (0, -speed3 * Time.deltaTime, 0);		
		if (startCar3.transform.position.y < -9){
			startCar3.transform.position = new Vector3 (-1.05F, 8, 0);
		}

		startCar4.transform.Translate (0, -speed4 * Time.deltaTime, 0);		
		if (startCar4.transform.position.y < -9){
			startCar4.transform.position = new Vector3 (-0.35F, 8, 0);
		}

		startCar5.transform.Translate (0, speed5 * Time.deltaTime, 0);		
		if (startCar5.transform.position.y > 9){
			startCar5.transform.position = new Vector3 (0.35F, -8, 0);
		}

		startCar6.transform.Translate (0, speed6 * Time.deltaTime, 0);		
		if (startCar6.transform.position.y > 9){
			startCar6.transform.position = new Vector3 (1F, -8, 0);
		}

		startCar7.transform.Translate (0, speed7 * Time.deltaTime, 0);		
		if (startCar7.transform.position.y > 9){
			startCar7.transform.position = new Vector3 (1.65F, -8, 0);
		}

		startCar8.transform.Translate (0, speed8 * Time.deltaTime, 0);		
		if (startCar8.transform.position.y > 9){
			startCar8.transform.position = new Vector3 (2.25F, -8, 0);
		}
		
	}
}
2

public GameObject startCar1;

void Start() {
    startCar1.tag = "Put_Tag_Name_Here";
}