Taking money out of a 401k for a down payment is not an exception to the 10% early withdrawal penalty. That exception only applies to taking money from a traditional IRA. So you are subject to the 10% penalty if you are younger than 59 1/2 as well as ordinary tax. The amount withheld was only an estimate, which must be reconciled with your other income and other withholding amounts.
The federal taxes withheld is only an estimate. There is not a exception to the early withdrawal penalty when using a 401(k) for a new home purchase. Only from an IRA.
There is no exception for a hardship withdrawal.
The federal taxes withheld will be entered on your tax return as a tax payment on your Form 1040 Line 25b. The taxable amount of the distribution will be entered on your tax return as ordinary income.
To enter, edit or delete a form 1099-R -
Click on Federal Taxes (Personal using Home and Business)
Click on Wages and Income (Personal Income using Home and Business)
Click on I'll choose what I work on (if shown)
Scroll down to Retirement Plans and Social Security
On IRA, 401(k), Pension Plan Withdrawals (1099-R), click the start or update button
Or enter 1099-r in the Search box located in the upper right of the program screen. Click on Jump to 1099-R