How can I make a Police GUI for my own Lightbar?

I'm creating a police car for my own, I created the light and I scripted them flashing but I don't know how to make a GUI that appears when a humanoid sits on the driver sit, that can control lights and siren. Please Help!

You can do this using Seat.Occupant (or VehicleSeat.Occupant)

local Seat = script.Parent.DriverSeat
Seat:GetPropertyChangedSignal("Occupant"):Connect(function()
	local Driver = game:GetService("Players"):GetPlayerFromCharacter(Seat.Occupant.Parent)
	--The Driver is the player in the Seat
	--Put here the code you want :)
end)

Seat.Occupant returns the Driver's Humanoid