After you file

Schedule 3 line 12 f says to add lines 12a-12e.  That gets added to line 13 and goes on the 1040 form line 31.

There is a worksheet to calculate the line 12e amount that is found on the 1040/1040SR Worksheet Part II.

Do NOT amend until the IRS completed the original and you receive any refund.   If you amend and there are two tax returns in the system at the same time then both will be red flagged for inspections which can delay process for up to a year.

The worksheet is also found in the 1040 instructions page 105.

https://www.irs.gov/pub/irs-pdf/i1040gi.pdf