game.ReplicatedFirst.ScreenGui.Enabled = true
Yep just that
The script is also inside the screen GUI in replicated first
wait(10) game.ReplicatedFirst.ScreenGui.Visible = true
Make sure the Frame/GUI starts off as not visible
game:GetService("ReplicatedFirst"):WaitForChild("ScreenGui").Enabled = false
This is the best way I know of ^
WaitForChild, as it says in the name, waits until it finds a child named "ScreenGui" where you tell it to search for it, faster than just wait(10).
Also you should also use game:GetService(service) instead of game.Service, if something went weird like an exploiter renamed a service somehow it should still work because it's looking for the class name instead of the instance name of the service