How would I rotate this part so it's always pointing at mouse?

I have this code:

local Camera = game.Workspace.CurrentCamera

local part = script.Part


game:GetService('RunService').RenderStepped:connect(function()
	part.Parent = Camera
	part.CFrame = Camera.CoordinateFrame * CFrame.new(0,-2,-2)
end)

Which puts a part in the screen so it sticks blah blah, and I want to rotate it so it's pointing at the mouse, because as of the code it just is pointing horizontally off the screen. What would I do for that?

Your solution is really simple. Just use the CFrame constructor CFrame.new(Vector3 position, Vector3 lookAt).

--get the correct positioning
part.CFrame = Camera.CoordinateFrame * CFrame.new(0,-2,-2)

--rotate it, keeping the position we just set
part.CFrame = CFrame.new(part.Position, mouse.Hit.p)