If you haven't actually filed at all, you can open the return back up and change the filing method.
- Log into your account, and at the Tax Home or in the section "Your Tax Returns & Documents" for 2019, look for a link "Add a State."
- Click on "Add a State." (That doesn't really add one; that's just to open the return.)
- Once the return is open, go through the REVIEW section to be sure everything is still in order.
- Then go to the FILE section and change the filing method to efile.
- Then continue on answering all the remaining screens and at the final step click a big orange button "Transmit Returns Now."