At this point, you can't. You can't amend an income tax return until the IRS has accepted the income tax return and fully processed it.
Even if the income tax return hasn't been accepted by the IRS yet - "officially" the IRS will begin pulling income tax returns off TurboTax servers 1/29/19 - it can't be fetched back off TurboTax servers and fixed. Pressing that "E-file" button is just like dropping a paper copy of your income tax return in a stamped envelope into the mail slot of your local post office. It's gone.
IF, when the IRS does take your income tax return off TurboTax's servers, they "reject" your income tax return and bounce it back to you, THEN at that point you can enter that 1099-R, and fix whatever else caused the income tax return to be rejected, and re-file.
IF the IRS does accept your income tax return when they pull it off TurboTax's servers THEN you must wait until they've completed their processing and sent you your refund before you can officially "amend."
Amending an income tax return can only by done by mail, there's no e-filing of Form 1040X.
Start here
http://turbotax.intuit.com/support/iq/Amend-a-Return/How-to-Amend--Change-or-Correct--a-Return-You-A...
to understand how you do amend the income tax return.
Tom Young
