How would I make a Custom Loading Screen for this?

Does anyone know how I'd make a custom loading screen for a script using ReserveServer? I read the wiki page and tried it but it still didn't work, here's the script I am using:

while true do
print("success")
wait()
repeat
wait()
until game.Players.NumPlayers >= 5

wait(25)
local TeleportService = game:GetService("TeleportService")
local destinationPlaceId = 2163624217

local reservationCode = TeleportService:ReserveServer(destinationPlaceId)

local players = game:GetService("Players"):GetPlayers()
wait(5)
TeleportService:TeleportToPrivateServer(destinationPlaceId, reservationCode, players, game.ReplicatedStorage.LoadingGui)
end

There is probably something wrong with this, could anyone help me fix it?