Have you signed the return but have not actually submitted it by either printing and mailing, or by efiling?
If you haven't actually submitted anything, you can go through the FILE section again to change the filing method, check direct deposit info, etc.
If you've already paid, you can also print out a copy of your return to review prior to filing, no matter if you are mailing or if you are efiling.
If you haven't filed, but TurboTax thinks you are finished, here's how to open the return back up:
Log in and at the section "Your Tax Returns & Documents" look for a little box with a link that says "Add a State." That doesn't really add one, but opens the return back up.
