Where would I put this anti-walkspeed script in the game to make it work?

Where should I place this?

local MaxSpeed = 16 -- Max speed possible in game
 
-- Note: I've added a rule-counter, which means you have to go too fast for 2 ticks to get punished.
-- That's necessary for teleporting by spawning, maybe your admins tp'ing, entering a vehicle, ...
 
local caught = {}
local function punish(plr)
	if caught[plr] then
		-- More than 2x too fast in a second? Seems like he needs to get punished
		-- (As far as I know, it's impossible to teleport 2x in a second without exploiting)
		-- (Assuming that people don't use admincommands teleport/ very fast)
		-- (Also assuming that the game doesn't teleport someone 2x in a second)
		if tick() - caught[plr] < 1 then
			-- Should never fail, as we don't check RobloxLocked players
			-- Even if it fails, punish() is called in a pcall() so it's safe anyway
			plr:Kick()
			print(plr,"kicked for speed hacking") -- Print in Server Console
		end
	end caught[plr] = tick()
end
 
-- We don't want to flood the caught table with offline exploiters who were here, don't we?
game:GetService("Players").PlayerRemoving:connect(function(p)
	caught[p] = nil -- remove old unneeded data
end)
 
local function ignoreState(state)
	if state == Enum.HumanoidStateType.Running then
		return false
	elseif state == Enum.HumanoidStateType.RunningNoPhysics then
		return false
	elseif state == Enum.HumanoidStateType.StrafingNoPhysics then
		return false
	elseif state == Enum.HumanoidStateType.Climbing then
		return false
	elseif state == Enum.HumanoidStateType.RunningNoPhysics then
		return false
	end return true
end
 
while true do
	--[[ Saving the current position (position just before the tick change) ]]--
	local pos = {}
	for k,v in pairs(game:GetService("Players"):GetPlayers()) do
		if v.Character and v.Character:findFirstChild("Torso") then
		    -- Renamed/Absent Humanoid? Oh well, can't predict that
			if not v.Character:findFirstChild("Humanoid") then return end
			local human = v.Character.Humanoid -- need to use it a lot
			-- Torso can be flinged away on dead, making false results
			if human.Health == 0 then return end
			-- If he sits, we assume he's in a vehicle, thuss may go faster
			if human.Sit then return end
			-- If he's platformstanding, we assume he's skating or so
			if human.PlatformStand then return end
			-- only check if the player is actually running
			if ignoreState(human:GetState()) then return end
			-- Save current position, for comparing during the next loop
			pos[v] = v.Character.Torso.Position
		end
	end
 
	--[[ Max Distance Calculation ]]--
	local tim = wait() -- Get how long the last tick happened
	local dis = (MaxSpeed + 2) * tim -- Get the max distance someone can move in that time interval
	-- (MaxSpeed + 2): 2 being a safe margin. (Weird calculation? Jumping while running?)
 
	for k,v in pairs(pos) do -- Time to see if he went too fast
		pcall(function()
			if v.Character and v.Character:findFirstChild("Torso") then
				if not v.Character:findFirstChild("Humanoid") then return end
				local human = v.Character.Humanoid
				if human.Health == 0 then return end
				if human.PlatformStand then return end
				if human.Sit then return end
				if ignoreState(human:GetState()) then return end
				-- Yeuy! Get the distance calculated!
				local d = (pos[v] - v.Character.Torso.Position).magnitude
				if d > dis then pcall(punish,v) end
			end
		end)
    end
 
    wait(0.1) -- Just to make this a bit more performance-friendly
    -- (Not that it's very unfriendly, though, unless there are 100 players)
end