To file an additional return using TurboTax Online,
you will need to create a new account. Please see the following TurboTax
FAQ for instructions on how to start another return using TurboTax Online.
If you have several returns to file, you may be interested in purchasing
a TurboTax CD/Download, as you can e-file up 5 federal returns for no
extra charge, whereas you will be charged for each return (unless eligible for
free filing) using TurboTax Online.
https://ttlc.intuit.com/replies/3288574
If you are filing another return to report other tax
documents for yourself, be aware that you file all of your W-2 and other tax
documents on one return for each tax year. If you need to add anything to your
return, you will need to amend your original return to include anything that
wasn't on the original return.