If you e-filed the extension request then you had to use the TurboTax online editions. If you started a 2018 tax return with the online editions, then you can download the tax data file and continue the tax return with the desktop edition you purchased.
To access your current online tax returns sign onto the TurboTax website with the userID you used to create the account - https://myturbotax.intuit.com/
See this TurboTax support FAQ for saving the tax data file from the online edition to your computer - https://ttlc.intuit.com/community/saving/help/how-do-i-save-my-turbotax-online-return-as-a-tax-data-...
Start the TurboTax desktop software. Click on the File menu at the top left of the program screen. Click on Open Tax Return. Browse to the location where you downloaded the tax data file.
