Do you mean you started a 2018 return last year using online TT?
Many people have multiple TT accounts and forget how to access them. Log out of the account you are in now.
Account recovery
https://myturbotax.intuit.com/account-recovery/
https://ttlc.intuit.com/questions/1901535-forgot-your-turbotax-online-user-id-or-password
Or did you use the desktop version of TurboTax? If so, the files are on your own hard drive or any backup device you used like a flash drive.
https://ttlc.intuit.com/questions/1901486-how-many-turbotax-accounts-do-i-have
https://ttlc.intuit.com/questions/1901535
Now it is too late to use online software or to e-file. If you have any changes/corrections at all to make to your 2018 return, you now have to complete it using desktop software, which you must download to a full PC or Mac (not to a mobile device).
https://ttlc.intuit.com/questions/2559403-how-do-i-finish-a-prior-year-return-that-i-started-in-turb...
If you already paid for your online software you can ask customer support for a download of the desktop software.
They are available from 5 a.m. to 5 p.m. Pacific time Monday-Friday.
https://ttlc.intuit.com/questions/1899263-what-is-the-turbotax-phone-number
If you are getting a refund, there is no penalty for filing late. If you owe tax due, then file and pay the amount due as shown on the Form 1040, but expect a bill later from the IRS for the penalty and interest you will owe. Only the IRS will calculate this—TurboTax will not calculate it.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**