How to use InputBegan and InputEnded in this one?

I want to script it so that when I press R the ball will slowly go bigger and when i unpress R it will throw it~~~~~~~~~~~~~~~~~

UIS.InputBegan:Connect(function(Input, isTyping) if not isTyping then

if Input.KeyCode == Enum.KeyCode.R and not debounce then
	debounce = true
		fireball:FireServer(player:GetMouse().Hit.p)
		print(player:GetMouse().Hit.p)
		wait()
	debounce = false
	end 

end

end)

UIS.InputEnded:Connect(function(Input, isTyping)

if not isTyping then
	
	if Input.KeyCode == Enum.KeyCode.R and not debounce then
		
		
	end
end

end)

I do not know what to write in 

local fireball = game:GetService("ReplicatedStorage"):FindFirstChild("fireball")

fireball.OnServerEvent:Connect(function(player, mousePos)

local character = player.Character

local fireball = game:GetService("ReplicatedStorage"):FindFirstChild("Fireball"):Clone()
fireball.Parent = game.Workspace
fireball.Size = Vector3.new(2, 2, 2)
fireball.CFrame = character:WaitForChild("HumanoidRootPart").CFrame * CFrame.new(0, 10, 0)
fireball.Massless = true

local TweenService = game:GetService("TweenService")
local Info = TweenInfo.new(3, Enum.EasingStyle.Bounce, Enum.EasingDirection.Out, 0, false, 0)
local properties = {
	Color = Color3.fromRGB(255, 0, 0),
	Size = Vector3.new(15, 15, 15),
	Anchored = true
}
local Tween = TweenService:Create(fireball, Info, properties)
Tween:Play()
Tween.Completed:Wait()
fireball.Anchored = false

local bv = Instance.new("BodyVelocity", fireball)
bv.Velocity = CFrame.new(fireball.CFrame.Position, mousePos).lookVector * 50
bv.MaxForce = Vector3.new(math.huge, math.huge, math.huge)

end)

This line already makes it bigger but I dont know how to put it to InputBegan as it will error

Thanks in advance!