how do i get what the player has selected in the EditorUtility Window?

hello, so today i've been trying to make a script that basically makes the player be able to import a 3d model (only one) as a mod, but i can't seem to get the file that the player has selected, it only instantiates the object that has the script on, if you want to help me, the script is this:

Code (CSharp):

1.  
2. using System.Collections;
3. using System.Collections.Generic;
4. using UnityEngine;
5. using UnityEngine.UI;
6. using System.IO;
7. using UnityEditor;
8.  
9. public class openFileSelector : MonoBehaviour
10. {
11.     public GameObject LockedCube;
12.     void Apply()
13.     {
14.         Object obj = Selection.activeObject as Object; //this is where i try to get the selected 3d model that the player selected.
15.         if (obj == null)
16.         {
17.             EditorUtility.DisplayDialog("Select Map", "You must select an FBX first!", "OK");
18.             return;
19.         }
20.  
21.         string path = EditorUtility.OpenFilePanel("Overwrite with FBX", "", "fbx");
22.         if (path.Length != 0)
23.         {
24.             var fileContent = File.ReadAllBytes(path);
25.             Instantiate(obj); //this is where i try to instantiate the selected 3d model but instead it instantiates the gameobject that the script is put on.
26.             Destroy(LockedCube);
27.         }
28.         gameObject.GetComponent<openFileSelector>().enabled = false; //to prevent people from abusing the importing 3d model stuff.
29.     }
30.     void Start() {
31.         Apply();
32.     }
33.     void Update()
34.     {
35.  
36.     }
37. }

EDIT: i think i posted this in the wrong thing lol