How do I make it so when you die it says something on the screen?

It's confusing to me.

While ATestAccount420's answer would probably work, I would recommend using the .Died event.

local player = game.Players.LocalPlayer
repeat wait() until player.Character
local hum = player.Character:WaitForChild("Humanoid")

hum.Died:connect(function()
	-- insert whatever you want in here
end)

This way, you are able to do other things in your script, without messing with spawn() or coroutines.

You'd do something like this, ofc you could customize the gui to how u like it but yeah.

local plr = game.Players.LocalPlayer
local dead = false

while true do
     if plr.Character.Humanoid.Health == 0 and dead == false then
    local guithingyidk = Instance.new('ScreenGui', plr.PlayerGui)
      local Text = Instance.new('TextLabel', guithingyidk)
      Text.Position = UDim2.new(0.5,0,0.5,0)
      Text.Text = "You Are Dead"
      Text.TextColor3 = Color3.new(1,0,0)
      Text.TextSize = 100
     dead = true
      wait(6)
     dead = false
     end
wait()
end