Enter information about annuities. Do not enter information about Social Security benefits, pensions, or retirement accounts, such as 401k or Roth accounts -- there are other areas to enter that information.
Also, in the Settings and Assumptions section you can control annuitization of assets that are in your retirement accounts, so generally you should only enter an annuity in the Annuities section if it is not from assets in your retirement accounts.
See also: Entering Annuity