I'm using the TurboTax free edition. Where can I find the form 1040-ES form section, so I can fill this out?

You do not "fill out" a 1040ES section.    When you print out your tax return it might print out those 1040ES vouchers.  They are optional to use.   If you expect to owe at least $1000 at tax time next year, it can be a good idea to use those forms to mail in with a check or money order to make estimated quarterly payments to avoid a big tax bill next year.  You do not have to use them----it is up to you.

Or do you need to enter 1040ES payments you sent in last year?  You probably need Deluxe to enter those.  

To enter Federal or State Estimated Taxes Paid, including a state estimated payment made in January for the prior year, go to

Federal on left or at top. Personal (Home & Business)

Deductions and Credits

Then scroll way down to Estimates and Other Taxes Paid

Estimated - click the Start or Update button