I contributed $2,520.19 in 2019 to a backdoor Roth but was unaware that it was something that needed to be on the 2019 return. What steps do I need to take to amend?

I need to know how to amend my 2019 return and also what steps to take to do this properly for 2020?  I have a Form 1099-R from my financial institution for both years.