Downloading assets from internet.

In may game user can change cloths of character but I want to updates the new clothes via internet.

You haven’t asked a question, but the answer is probably the WWW class:

using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    public string url = "http://yourserver.com/yournewclothes.jpg";
    IEnumerator Start() {
        WWW www = new WWW(url);
        yield return www;
        renderer.material.mainTexture = www.texture;
    }
}