Plugin interface not working? Error: attempt to index nil with 'WaitForChild'

So i tried to make a a dockable plugin gui the only problem is: whenever i click the plugin it makes a big windows with the correct sizes but it doesnt move the gui. Keep in mind the gui i am trying to move is an image label that has the buttons in it. Here is the script:

local toolbar = plugin:CreateToolbar("Wand Configurer")
local PluginButton = toolbar:CreateButton("Wand Configurer","Configure the wands","")

local interface = plugin:CreateDockWidgetPluginGui(
	"Make Script",
	DockWidgetPluginGuiInfo.new(
		Enum.InitialDockState.Float,
		true,
		true,
		564,
		390,
		564,
		390
		)
)

local top = script:WaitForChild("Top")
local bottom = script:WaitForChild("Bottom")
interface.Title = "Wand Configurer"
top.Parent = interface
bottom.Parent = interface

That’s because just scripts are saved as .lua files in user directories, or something like it. Enclose your script in a model or folder and save the model or folder as the plugin.

https://devforum.roblox.com/t/a-guide-to-plugin-guis-lua-widgets/129712/9