Once
you've signed into TurboTax and opened your return in progress, click on
the Federal Taxes tab,
then select Wages &
Income, then scroll down the page to the various income sections (you may need to click on "Skip to see all income" to display those section headings).
Select Retirement Plans & Social Security, then click on Social Security (SSA-1099, RRB-1099) to open that section. Then just follow the
prompts.