How do I make my Fireball go to where my Mouse points?

local StarPack = game:GetService("StarterPack")
local RepStore = game:GetService("ReplicatedStorage")

StarPack.FireballF.OnServerEvent:Connect(function(plr)
    local char = plr.Character
    local x = RepStore.Fireball:Clone()
    x.Parent = workspace
    x.CFrame = char.UpperTorso.CFrame * CFrame.new(0,0,-4)
    x.CanCollide = false
    local v = Instance.new("BodyVelocity")
    v.Parent = x
    v.MaxForce = Vector3.new(math.huge, math.huge, math.huge)
    v.Velocity = 
end)

local UIS = game:GetService("UserInputService")
local StarPack = game:GetService("StarterPack")
Ammo = 1

UIS.InputBegan:Connect(function(input)
if Ammo == 1 then
    if input.KeyCode == Enum.KeyCode.F then
        StarPack.FireballF:FireServer()
            Ammo = Ammo-1
            wait(2)
            Ammo = 1
        end
    end
end)

The first is the Script, the second is the Local Script v.Velocity should go to where the mouse points