The script in serverscriptservice:
local Frame = Instance.new("Frame")
local ScreenGui = Instance.new("ScreenGui")
local StarterGui = game.StarterGui
ScreenGui.Parent = StarterGui
Frame.Parent = ScreenGui
Frame.Position "{0, 0},{0, 0}"
Frame.Size "{0, 100},{0, 100}"
if Frame.Visible == false then
Frame.Visible = true
end

2 comments
The frame and screen gui shows in StarterGui but not on my screen?!
in line 3 do local StarterGui = game.Players.LocalPlayer.PlayerGui and make it in local script (i dont know if it works but you can try)