Investors & landlords

Hello, sorry to bother you again... just wanted to correct my previous findings.  For installment sale of  my property in  2017, the actual entire capital gain was $24,050 and I already claimed $19,950 at year 1. So, year 2018, where and how I can enter the remaining gains $4100.  Apparently, I did it wrong in 2018.  I need to fix it.  I understand where the interest goes.  I am confused by following the steps actually.  It will ask me if I have installment Sale in 2018 which I did not.  In my original 2018 tax return, I answered Yes.  That is wrong.