If TurboTax thinks you were finished and were going to print and mail, your return interview will need to be opened to change the filing method. To do that, log in and go to the Tax Home (it may open at the Tax Home already). Then to open the interview click on the link "Add a State." That won't really add one, but will open the interview back up. Then once inside your return, go to the REVIEW tab to see if there is anything preventing you from efiling. Then go to the FILE section and change the filing method from print/mail to efile.
If you get some error message in regards to efiling, post in the forum describing the problem in detail, and someone may be able to tell you what to do.
Also be aware that while it is technically possible to efile now, the IRS has not yet opened up to start processing 2020 returns. They will open for processing on February 12, 2021. If you efile before then, your return will sit on TurboTax servers in "pending" status until the IRS starts pulling returns on February 12. The IRS pulls a very small number of returns early for testing purposes, but for most people it will be February 12 or soon after.
A common error some people get when efiling this early is that one or more forms may not yet available for efiling. When you go through the REVIEW tab, it should tell you if any of your forms are not yet available. Here are tables that show availability dates for various forms in the Federal and state returns.
TurboTax IRS Federal Forms Availability Table:
State Forms Availability Table: