Incorrect use of GetPlayerFromCharacter() ?

I tested my game and instantly saw an error about Argument 1 missing or nil

Here's the script (The problem is Line 1)

local Playar = game.Players:GetPlayerFromCharacter()
local Start = Playar.PlayerGUI
--[[local RobuxGUI = game.ReplicatedStorage["R$GUI"]:Clone()
		RobuxGUI.Parent = Start]]


script.Parent.Touched:connect(function(Hit)
	local Character = Hit.Parent
	if Start["R$GUI"] ~= nil or Start["HelpGUI"] ~= nil then
		print("")
	elseif Start["R$GUI"] == nil or Start["HelpGUI"] == nil then
		local RobuxGUI = game.ReplicatedStorage["R$GUI"]:Clone()
		RobuxGUI.Parent = Start
	end
end)

If I'm using this GetPlayerFromCharacter function wrong, may I be given an example or something to help?

I would like to add that

 if parent.child ~= nil then

won't work.

Before you check if it doesn't equal nil, you're already assuming there actually is an object to check! While checking if it exists, you're already assuming that "it" does indeed exist. If "it" doesn't exist, you just indexed a nil value, and the script will error.

You need to use the FindFirstChild() method. It will look for the child, and return that child if it exists. If not, it will return nil. Since it works like a function, instead of throwing an error it will simply become nil.

if parent:FindFirstChild("child") ~= nil then