As I understand from your question, you are trying to activate a GUI when you click a Part.
script.Parent.ClickDetector.MouseClick:Connect(function(player)
player:WaitForChild("PlayerGui").ScreenGui.Frame.Visible = true
end)
--[[
Replace ScreenGui with your GUI name.
--]]
Do not use a LocalScript for MouseClick event.
Also, please read About the Art Design Support category.
This thread should be in #development-support:scripting-support.