How can I make a trail gamepass?

I want to make a gamepass that can give players some sort of a trail. I have tried the following script. Here is what i've worked with.

local passId = 1061598200 --change this to your GamePass Id
local marketplaceService = game:GetService("MarketplaceService")

marketplaceService.PromptPurchaseFinished:connect(function(player,assetId,isPurchased)
    if isPurchased then --if the player did pay
        if assetId == passId then --if what they bought is the pass
            Instance.new(“Trail”,char.Torso)

        end
    end
end)``

I have no idea how to make the trail or the trail gamepass work. Immediate help would be appreciated.