Billboard GUI positioning/scaling problems?

I was trying to try out billboard GUIs and ran into some problems. The are not like regular GUIs and I have no idea how to center one Frame to into another Frame if the hierarchy is BillboardGUI => Frame => Frame (=> means 'parent of')

For some reason, I can't change any property of the Frames when I launch Solo or Server Test This is my code

game.Players.PlayerAdded:Connect(function(player)
    local boardclone = board:Clone()
    local background = boardclone:WaitForChild("Background")
    local energy = boardclone:WaitForChild("Energy")

    background.BorderSizePixel = 0
    background.Size = UDim2.new(1, 0, 1, 0)
    background.BackgroundColor3 = Color3.new(0,0,0)
    background.Style = Enum.FrameStyle.RobloxRound

    energy.Size = UDim2.new(.95, 0, .95, 0)
    energy.BackgroundColor3 = Color3.new(0, 255, 0)
    energy.Position = UDim2.new(.5, 0, .5, 0)
--  boardclone.Parent = game.Workspace[player.Name].Head
end)