How do I make this locate a players head?

Here's your script fixed up. I'd insert a Hat Insert model into my place, Test it in Play Solo, enter the ID, pick up the hat, then bring it to Lightning and in my script, it'd just clone it and parent it. Your way should work.

local passId =  161403364

function isAuthenticated(player)
    return game:GetService("GamePassService"):PlayerHasPass(player, passId)
end

game.Players.PlayerAdded:connect(function(plr)
    plr.CharacterAdded:connect(function(char)
    if isAuthenticated(plr) then
        print(plr.Name .. " has bought the game pass with id " .. passId)
Instance.new("Hat",game.Workspace.Lighting)
h = game.Workspace.Lighting.Hat
Instance.new("Part",game.Workspace.Lighting.Hat)
Instance.new("Mesh",game.Workspace.Lighting.Hat.Part)
h.MeshId = "rbxassetid://1031429"
h.TextureId = "rbxassetid://1031417"
local Model = game.Workspace.Lighting.Hat
Model.Parent = char.Head
    end
end)
end)