What are you trying to enter about the car? Why do you think you need to enter anything about Grandma buying you a car? Gifts are not taxable so you do not have to enter anything about it on your tax return.
If your grandmother paid more than $15,000 for the car for you then she will need to prepare a gift tax form--but she will not owe any tax.
Money that you receive as a gift is not taxable income to you, and you do not need to report it on your income tax return. Money that you gave as a gift to someone else is not deductible for your taxes.
Turbo Tax does not support the gift tax form 709, but here is a link:
You do not have to report this on your income tax return.
Your grandmother might have to file a gift tax return if the car and any other gift you received from her were more than the annual gift exclusion of $15,000. Please see Frequently Asked Questions on Gift Taxes.
**Mark the post that answers your question by clicking on "Mark as Best Answer"