You do not have to enter anything about your 401k unless you took money out in 2019. If you have a 401k at work, information about it is entered when you enter your W-2--from Box 12. You do not enter it again.
IF you took an early withdrawal or have begun receiving monthly income from the 401k, you will get a 1099R to enter.
To enter your retirement income, Go to Federal> Wages and Income>Retirement Plans and Social Security>IRA 401 k) Pension Plan Withdrawals to enter your 1099R.