After you file

First the 1040X is a generic form where you enter the tax year at the top ...   https://www.irs.gov/pub/irs-pdf/f1040x.pdf

And you will fill in only columns A & C with the same amounts and leave column B blank.  Then put the reason for filing it on page 2  along with a signature and attach the form 8606 to it ... mail each tax year separately.