I chose to pay by check, but now I have decided to pay electronically. how do I make that change?

You can pay in whatever way you choose to.  TurboTax never knows how, when or even if you pay your tax due.  TT is not monitoring whether you pay.

Go to www.irs.gov and set up an account. There some hoops to jump thru to establish your ID. After that, logging is if fairly easy with 2-step authentication. In your account, you may see an amount due of $0 if IRS has not processed your return. You can click "Make Payment" and it will give you the option to make your payment that you expect to be due on your return and select the direct from bank option. You could try setting up an account with your state as, and they may let you make a payment online for an unprocessed state return as well. Good luck!

To change payment method if you haven't already filed your return:

1. Sign in to your account and open or continue your return.
2. Select File in the left menu and proceed to the Just X more steps screen.
3. On this screen, select Revisit next to You've chosen to deduct your TurboTax fees from your federal refund.
4. Select View Payment Options on the next screen and select Pay now on the screen after that.
5. Complete payment by entering your credit or debit card information.
6. Continue to the Just X more steps screen to make sure the Pay With My Refund has been removed.
7. Step 1 on the screen should now show that you paid with your credit or debit card.

TurboTax FAQ: How do I remove Pay With My Refund fees in TurboTax Online and change my payment method?

If you have already e-filed (or even if you haven't): You can go to the IRS Make a Payment website and Make a Payment there via credit card, debit card or Direct Pay.