How to make 2nd tax payment on covid-19 401-k withdrawal from 2020

I made covid-19 penalty free 401K and IRA withdrawals in 2020 and elected to pay the tax over 3 years.  I made the first tax payment on my 2020 tax return which I filed in 2021.  The 2020 tax return included form 8915E.  I have no idea how to make the 2nd tax payment when filing my 2021 tax return.  I though it would come up in disaster relief.  Can someone please explain exactly how I make my next tax payment for the deferred 401K / IRA income.