How do i make my chat window save messages and be a scrolling GUI

Ok so i just made a 3d text over my character and when you type a message it pops up over their head. Now what i want to do is have that message logged in the ui we have preset on the screen as well as have the gui have a scroller so i can see old messages. All my code is working but here is what I have as of right now.

 using UnityEngine;
 using System.Collections;
 
 [RequireComponent (typeof(GUITexture))]
 
 public class ChatWindowPlacement : MonoBehaviour {
     public GUIStyle style;
     private GUITexture Image;
     private int Screen_width;
     private int Screen_height;
     public string stringToEdit = "";
     public TextMesh speechBubble;
     void Start () {
         Screen_width = Screen.width;
         Screen_height = Screen.height;
         Image = guiTexture;
         Image.pixelInset = new Rect (Screen_width / 100, Screen_height / 100, Image.pixelInset.width, Image.pixelInset.height);
     }
     
     // Update is called once per frame
     void Update () {
     
     }
     
     void OnGUI() {
         
         stringToEdit = GUI.TextField(new Rect(Screen.width /60f,Screen.height / 1.05f, 300,20),stringToEdit,25);
         if(Input.GetKeyDown(KeyCode.Return))
         {
             speechBubble.text = stringToEdit; 
         }
         if(GUI.Button( new Rect(Image.pixelInset.x + Image.pixelInset.width / 1.1f, Screen_height - Image.pixelInset.y - Image.pixelInset.height + Image.pixelInset.height/ 20, Image.pixelInset.width / 15, Image.pixelInset.height / 10) , "", style) ){
             Debug.Log("Closing Chat");
             gameObject.SetActive(false);
         }
     }
 }