If the only income you received during the year was your Social Security or equivalent tier 1 railroad retirement benefits, your benefits generally are not taxable and you probably do not have to file a return.
Your social security benefits will not be taxed unless your adjusted gross income is generally equal to one half of your social security payments plus all your income from other sources.
The software will figure this amount for you based on your inputs. The Social Security Benefits Worksheet will appear in the forms list when viewing.
For more information, see page 32 of the form 1040 instructions for 2018.