At this stage, you will need to wait until IRS accepts your electronic return before amending your 2020 return. According to IRS.gov, IRS will not begin accepting returns until 02/12. Once your return is accepted:
In your landing page, scroll down to the bottom of the page. You will see an option to amend (change) 2020 return. Do not attempt this now because that option won't be available until IRS accepts your return.
Once you are in the amendment process, go to:
federal>income and expenses>all income
Retirement plans and Social Security>show more
Social Security (SSA-1099, RRB-1099) Start
Here you will enter your SSA-1099.
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