How to make a start GUI?

Like so, when you enter the game you just click the screen with the start button to begin with a picture on the screen?

You can use the PlayerAdded event in Players to tell when a player was added and then make a gui visible for that player. For example:

game.Players.PlayerAdded:connect(function(np)
	np.PlayerGui.ScreenGui.Gui.Visible=true
end)

Search up start GUI in free models then customize it

Add a GUI into the StarterGui so when a player enters, the GUI appears on their screen. Put this script inside the enter/begin/etc button to remove the GUI:

script.Parent.MouseButton1Click:connect(function(mouse)
if mouse then
script.Parent.Parent.Visible = false
end
end)

The hierarchies should look like this:

ScreenGui -Frame -TextButton -Script

Hope this helps.