Need help with moving object script (C#)

Hi guys,

I need help with a simple script that moves a object down the y axsis in a specific speed. I dont where to start. Any help would be great.

Thank You

Script

using UnityEngine;
using System.Collections;

public class CoinMovement : MonoBehaviour {

public float speed = 1.0f;
public string axisName = "Vertical";
// Use this for initialization
void Start () {

}

// Update is called once per frame
void Update () {
	transform.position += 
}

}

I don’t know where to start”.

Here: http://unity3d.com/learn/tutorials/modules/beginner/scripting/translate-and-rotate