Form 709 is not part of an income tax return. You do not include it with your Form 1040. And...TurboTax does not support Form 709.
Gifts given to family members, friends or other individuals are not deductible. Gifts received are not taxable to the person who received the gift, and are not entered on a tax return.
If your gift exceeds the yearly limit ($19,000 per individual) imposed by the gift tax rules, then you will need to complete a Form 709 gift tax form and send it to the IRS, although it is very unlikely that you will owe any tax.
TurboTax does not support Form 709. It is not an income tax form and would not be included as part of an income tax return.
Here is a link to the form:
https://www.irs.gov/pub/irs-pdf/f709.pdf
https://turbotax.intuit.com/tax-tips/estates/the-gift-tax-made-simple/L5tGWVC8N
Here's a link for Form 709 preparation software:
https://www.puritas-springs.com/product-category/federal
Here are some useful videos on the Form:
https://www.youtube.com/watch?v=a5wJow5h-No
https://www.youtube.com/watch?v=5Z_28sVOrTY
The following is from the IRS Instructions for Form 709.
When To File
Form 709 is an annual return.
Generally, you must file Form 709 no earlier than January 1, but not later than April 15, of the year after the gift was made. However, in instances when April 15 falls on a Saturday, Sunday, or legal holiday, Form 709 will be due on the next business day.