how do you make particles appear on a player when they press a certain key?

I have gotten you an example script to show you how you can work with key press events.

This scripts detects when a button is pressed and if the button is f then it will make particles appear on the players head. I did have to use a remote event for this since clients cant make a new instance unless you want the particles only to be on their screen.

LOCAL SCRIPT (inside of startergui)

local plr = game:GetService("Players").LocalPlayer
local mouse = plr:GetMouse()

mouse.KeyDown:connect(function(key)
	if key == "f" then
		game:GetService("ReplicatedStorage").Key:FireServer()
	end
end)

SERVER SCRIPT

game:GetService("ReplicatedStorage").Key.OnServerEvent:connect(function(plr)
	local Particle = Instance.new("ParticleEmitter",plr.Character.Head)
end)

Enjoy! And if you have any questions please message me!