If you are a W-2 employee, then your contributions to the 401(k) are reported on your W-2 in box 12 with a code of D. Those contributions are not entered anywhere else on a tax return.
You can use the TurboTax free online edition if all you will be entering on the tax return is the tax data from your W-2.
Go to this TurboTax website for the Free online edition - https://turbotax.intuit.com/personal-taxes/online/free-edition.jsp