You should have received a 1099-R tax statement for this
transaction to be entered in the following area in TurboTax Online:
Click My Account (Top right of your screen).
Select Tools.
In the pop up window, select Topic Search.
In the search bar, type in 1099-r
Highlight it and select GO, and follow the prompts
If you rolled over your 401(k) to the Traditional IRA "trustee to trustee" (without ever having actually received a check) the rollover will not be taxable, but the 1099-R should be reported.