How do You add a Scrollbar in a textbox C# code

Hello I am currently working on a unity project that requires a textbox that would pop up when clicked on the game object, the problem im having is making the code i need to communicate with the c# file. 1: the code should allow the player to click on the game object that pops up a text box with a scroll bar inside and also the text that is generate can be edited by the user in the C# code. the text can only be added in the editor not the Script file. 2:the same format but without the Scollbar just editing the text in C#. Any help with this Greatly Apreciated, Below is the Script code im working on now .

public class DialogueBox : MonoBehaviour { private string myText = "You Have Arrived at your destination";

 // Use this for initialization
 private bool PopUp;
 public string Info;
 
 void OnMouseDown()
 {
     PopUp = true;
 }
 
 void DrawInfo()
 {
     Rect rect = new Rect (20,20, 300, 200);
     Rect close = new Rect (300,20,20,20);
     if (PopUp)
     {
         GUI.Box(rect, Info);
         if (GUI.Button(close,"X"))
         {
             PopUp = false;
         }
     }
 }
 
 void OnGUI()
 {
     DrawInfo();
 }

}