To enter your RMD you need to go to the 1099R section of Turbo Tax and go all the way through questions. It will ask RMD questions after you enter your 1099R:
Federal Taxes,
Wages & Income
(I'll choose what I work on - if that screen comes up)
Retirement Plans & Social Security,
IRA, 401(k), Pension Plan Withdrawals (1099-R).
OR Use the "Tools" menu (if online version left side) and then "Search Topics" for "1099-R" which will take you to the same place.