You should have received a 1099-R from your 401(k) plan administrator. Report this in TurboTax by navigating to Federal > Wages & Income >IRA, 401(k), Pension Plan Withdrawals (1099-R).
In order to ensure you pay the tax over a three-year period instead of one, and are exempt from the usual 10% penalty on early distributions, check the box I took out this money due to a qualified disaster after entering your 1099-R.