In TurboTax, go
through the File section until you reach the screen "How would you like to
pay your federal taxes?" You won't
see this screen if you owe $0, or are getting a refund.
Then, select "I
want to request an installment plan,"
"Continue," and follow the onscreen instructions.
Please see the IRS' Instructions for Form 9465
for line-by-line instructions. You can
follow along by looking at Form
9465.