How do I load my .dll Vehicle Menu

I am making a C# menu in which you can spawn custom cars put into the server. I have gotten everything setup, but when I build the project, I am given a .dll file. I have put it in my GTA V Script folder, FiveM Application Data Folder, and plugins folder in the FiveM folder. I tried to load it and press the button to open it, but I have not been able to open it.

I am using NativeUI and ScripthookVDotNet for my menu. I added the onKeyDown method and onTick method. Am I loading this completely wrong?

Important Code Below:

using System;
using System.Windows.Forms;
using NativeUI;
using GTA;

public class CarsMenu : Script
    {
        public CarsMenu()
        {
              Setup();
              Tick += onTick;
              KeyDown += onKeyDown;
        }

        void Setup()
        {
            menuPool = new MenuPool();
            mainMenu = new UIMenu("INSPRP Cars", "SELECT AN OPTION");
            menuPool.Add(mainMenu);

            //....

            mainMenu.OnItemSelect += onMainMenuItemSelect;
        }

        void onTick(object sender, EventArgs e)
        {
            if (menuPool != null)
                menuPool.ProcessMenus();
        }

        void onKeyDown(object sender, KeyEventArgs e)
        {
            if(e.KeyCode == Keys.F10)
            {
                mainMenu.Visible = !mainMenu.Visible;
            }
        }
    }

SHVDN isn’t supported by the client, you’ll have to set it up as a .NET resource that uses the CitizenFX.Core libraries, then use the NativeUI port for FiveM to create the menu.