The 1040SR is the same as the regular 1040 just larger type. Same line numbers. You automatically get the SR if you are 65. You can compare them,
1040 https://www.irs.gov/pub/irs-pdf/f1040.pdf
1040SR https://www.irs.gov/pub/irs-pdf/f1040s.pdf
If you use the Desktop program you can switch to forms and the Info Wks part II has a selection for 1040 or 1040SR.
