How to add particle effect and sound to double jumping?

Greetings! I have followed the Dev Forum Guide and have this script:

local UserInputService = game:GetService("UserInputService")
local localPlayer = game.Players.LocalPlayer
local character
local humanoid
 
local canDoubleJump = false
local hasDoubleJumped = false
local oldPower
local TIME_BETWEEN_JUMPS = 0.2
local DOUBLE_JUMP_POWER_MULTIPLIER = 2
 
function onJumpRequest()
	if not character or not humanoid or not character:IsDescendantOf(workspace) or
	 humanoid:GetState() == Enum.HumanoidStateType.Dead then
		return
	end
	
	if canDoubleJump and not hasDoubleJumped then
		hasDoubleJumped = true
		humanoid.JumpPower = oldPower * DOUBLE_JUMP_POWER_MULTIPLIER
		humanoid:ChangeState(Enum.HumanoidStateType.Jumping)
	end
end
 
local function characterAdded(newCharacter)
	character = newCharacter
	humanoid = newCharacter:WaitForChild("Humanoid")
	hasDoubleJumped = false
	canDoubleJump = false
	oldPower = humanoid.JumpPower
	
	humanoid.StateChanged:connect(function(old, new)
		if new == Enum.HumanoidStateType.Landed then
			canDoubleJump = false
			hasDoubleJumped = false
			humanoid.JumpPower = oldPower
		elseif new == Enum.HumanoidStateType.Freefall then
			wait(TIME_BETWEEN_JUMPS)
			canDoubleJump = true
		end
	end)
end
 
if localPlayer.Character then
	characterAdded(localPlayer.Character)
end
 
localPlayer.CharacterAdded:connect(characterAdded)
UserInputService.JumpRequest:connect(onJumpRequest)

And the question I am currently facing is, how would I go about adding a particle effect and a sound effect when doing a double jump? I wish to add this particle effect to the double jump https://www.roblox.com/library/7414413385/Puff

Help is much appreciated.

Well since you followed a tutorial and wrote the script, you already know where the second jump occurs.

You can just create a particle effect inside of the player attached to an attachment by the feet when a character is added, and then just enable and disable it.