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 += 
 }

}