how to put downloaded images into UIButton using UIToolkit

hi! i wonder how to put downloaded images inside a UI Button.

heres my code:

 using LitJson;
 using UnityEngine;
 using System.Collections;
 using System.Text;
 using Prime31;
 using System.Collections.Generic;
 
 
 public class LoadJSON_FBFriends : MonoBehaviour
 {
     
     private bool _movedContainer;
     public Material loadImageMaterial;
     
     private UIToolkit myToolkit;
     UIButton touchable,b1;
     
     private string userId;
     private Dictionary<string, string> friends;
     ArrayList friendsList;
     public GUIStyle friendsFontStyle;
     
     void Start()
     {
         
     var scrollable = new UIScrollableVerticalLayout( 0 );
     scrollable.alignMode = UIAbstractContainer.UIContainerAlignMode.Center;
         scrollable.position = new Vector3( 0, 3, 0 );
         var width = UI.scaleFactor * 800;
         scrollable.setSize( width, Screen.height / 0.10f );
         
         
         for( var i = 0; i < 13; i++ )
         {
             
     
             if( i == 13 ) 
             {
                 touchable = UIButton.create( "FriendsListBox.png", "FriendsListBox.png", 0, 0 );
                 
             }
             else if( i % 12 == 0 )
             {
                 touchable = UIButton.create( "FriendsListBox.png", "FriendsListBox.png", 0, 0);
             }
             else if( i % 11 == 0 )
             {
                 touchable = UIButton.create( "FriendsAvatar.png", "FriendsAvatar.png", 0, 0);
             }
             else if( i % 10 == 0 )
             {
                 touchable = UIButton.create( "FriendsListBox.png", "FriendsListBox.png", 0, 0 );
             }
             else if( i % 9 == 0 )
             {
                 touchable = UIButton.create( "FriendsListBox.png", "FriendsListBox.png", 0, 0 );
             }
             else if( i % 8 == 0 )
             {
                 touchable = UIButton.create( "FriendsListBox.png", "FriendsListBox.png", 0, 0 );
             }
             else if( i % 7 == 0 )
             {
                 touchable = UIButton.create( "FriendsListBox.png", "FriendsListBox.png", 0, 0 );
             }
             else if( i % 6 == 0 )
             {
                 touchable = UIButton.create( "FriendsListBox.png", "FriendsListBox.png", 0, 0 );
             }
             else if( i % 5 == 0 )
             {
                 touchable = UIButton.create( "FriendsListBox.png", "FriendsListBox.png", 0, 0 );
             }
             else if( i % 4 == 0 )
             {
                 touchable = UIButton.create( "FriendsListBox.png", "FriendsListBox.png", 0, 0 );
             }
             else if( i % 3 == 0 )
             {
                 touchable = UIButton.create( "FriendsListBox.png", "FriendsListBox.png", 0, 0 );
             }
             else if( i % 2 == 0 )
             {
                 touchable = UIButton.create( "FriendsListBox.png", "FriendsListBox.png", 0, 0 );
             }
             else 
             {
                 touchable = UIButton.create( "FriendsListBox.png", "FriendsListBox.png", 0, 0);
             }
             
             //loadImage(touchable, i);
             
             StartCoroutine(getImage(touchable, i));
             
             scrollable.addChild(touchable);
             
         }
 
     }
     
     IEnumerator getImage(UIButton uib, int i)
     {
 
         ConverterScript ss = new ConverterScript();
         
         string url = "https://graph.facebook.com/xxxxxxx/friends?limit=13&fields=first_name,picture&access_token=xxxxxx";
 
         WWW www = new WWW(url);
         yield return www;
         
         Texture2D tex = new Texture2D(128, 128);
         tex = www.texture;
         
         ProcessFriendsDisplay(www.text);
         
         uib.manager.renderer.material.mainTextureScale = new Vector2(18.0f, 20.4f);
         uib.manager.renderer.material.mainTexture = tex;
         
     }
 
     public void ProcessFriendsDisplay(string jsonString)
     {
 
         JsonData jsonFriends = JsonMapper.ToObject(jsonString);
         ConverterScript fbfriends = new ConverterScript();
         
         friendsList = new ArrayList();
         
         for(int i = 0; i<jsonFriends["data"].Count; i++)
         {    
 
             fbfriends.picture = jsonFriends["data"][i]["picture"]["data"]["url"].ToString();
             Debug.Log (fbfriends.picture + i);
 
         }
         
     }
     
 }