Are you using the Online version? Online is only good for one return per account. But you can use the same email address for 5 accounts. So don't use your account or you will overwrite your return.
Sign in or start a new account here,
https://turbotax.intuit.com/personal-taxes/online
The Desktop program can do unlimited returns and efile 5 federal for free. You can buy the Desktop CD or the Download program here,
https://turbotax.intuit.com/personal-taxes/cd-download
