Re: How can I add secondary phone number to my account?
Select the sim only plan you want with a new number then when you go to the checkout it asks if you already have an Optus My Account login. I would think it should be that simple. If in doubt speak with sales on the second link below and get them to do it for you.
Edit: I think I misread the question. You already have a second number and you want it transferred into your account? Is it an Optus number and is it in your name?