There's a certain way to record a lump-sum payment in Turbo Tax.
1. Click Federal on the left-hand side menu.
2. Click Income across the top.
3. Scroll down to Retirement Plans and Social Security and click Show more.
4. Click Start or Revisit by Social Security (SSA-1099, RRB-1099).
When you first get to the page, enter the Total Net Benefits from your form (box 5). Hit Continue.
You'll get to a screen (below).
You'll need your returns from each year that you have a lump-sum distribution for. It will be correctly calculated on your 1040.
Depending on your income in those prior years, you may have extra tax on your lump-sum, which will be payable in 2017.