How do you make a gamepass give a hat?

I need to be able to make a gamepass give the player a hat whenever they join, and put it automatically put it on their back (it's a swordpack)

See if this script can help you.

GamePassId = --YourGamePassId

game.Players.PlayerAdded:connect(function(Player)
	Player.CharacterAdded:connect(function() 
		if game:GetService("GamePassService"):PlayerHasPass(Player, GamePassId) then
			x = game.ServerStorage.YourBackSwords:Clone() --Save your "Swords" there <---
			x.Parent = Player.Character
			m = Instance.new("Motor6D", Player.Character.Head)
			m.Part0 = Player.Character.Head
			m.Part1 = x
			m.C1 = CFrame.fromEulerAnglesXYZ(0, 0, 0) *CFrame.new(0, 0, 0) --Play with the Position and Rotation of the Part
		end
	end)
end)