How to put a script on a button?

Question

Unity

It seems like a simple thing - to hang a script (function) on a button, I do it as described in the example, but the function does not appear

the script itself

using UnityEngine;
namespace Menu{
  public class UrlOpen : MonoBehaviour{
    public void OpenUrl(string url){
      Application.OpenURL(url);
      }
    }
  }

That is, in theory, I should have had a list of functions there from the script that I attached, but it's not there ...
Tell me what I'm doing wrong?

Answer 1

Hang the script on the object, throw this object into the cell under Runtime only