GUI not showing when inserted into PlayerGui?

Hi, I'm trying to get access to my GUI, so I can make changes, but I don't know how, because my script is located in StarterPack, because I'm making something with Tools, and I can't access StarterGui. I've tried inserting the GUI into the Player's PlayerGui which seems like the best option to do something like this, but it doesn't work. Can someone help?

Code:

local Tool = script.Parent
local GUI = Tool.GUI

Tool.Equipped:Connect(function()
  local Player = game.Players.LocalPlayer
  GUI.Parent = Player:WaitForChild("PlayerGui")
end)

local Tool = script.Parent
local GUI = Tool.GUI

Tool.Equipped:Connect(function()
  local Player = game.Players.LocalPlayer
  GUI.Parent = Player:WaitForChild("PlayerGui")
  GUI.Enabled = true
end)

the gui needs to be a ScreenGui if it isn't put it in a ScreenGui