Sign onto the TurboTax website with the userID you used to create the online account - https://myturbotax.intuit.com/
If you do not land on the screen that shows Take me to my return, then follow this procedure -
When you sign onto your online account and land on the Tax Home web page, scroll down and click on Add a state.
This will take you back to the 2018 online tax return to complete and file the tax return.