If you are using TurboTax Online, you'll need to create a new user ID and password (and pay again). It's better (and cheaper) to purchase TurboTax Desktop if you need to create multiple tax returns.
Only one return per taxpayer if using the online versions. Each must have a separate ID/password although you can use the same email address. To recover a previous account or get an emailed list of accounts tied to the same email address, see link below.