Facetime does not want to be used on my iTouch

I have bought recently an iPod Touch and when I go to set the email I will get "called" on, I use the email I have set up for the account. When I click on "NEXT" for the facetime Activation it tells me that email is already in use - well duh, its the email address I use for the Facetime on my Mac Laptop. It tells me that it is already in use. Its very frustrating.