Bilboard GUI not showing for some reason

Hello
I wanted to make an NPC using a bilboard gui like this:

I kinda don’t understand how GUI works or where it is stored inside the game.
First when I tried to make the bilboard gui a child of part that it adornees it didn’t show up so I figured out that I should be putting it inside the Starter Gui but it still didn’t show up.
I searched up the problem and I saw that I was supposed to enable the gui from a local script like this:

local player = game:GetService("Players").LocalPlayer
player.PlayerGui:WaitForChild("BillboardGui").Enabled = true

The problem is that when I run the game I get an error saying:

Infinite yield possible on ‘Players.Vol_Chaos.PlayerGui:WaitForChild(“BillboardGui”)’

It’s like it doesn’t exist when I play the game.
How am I supposed to fix this?