Non-deductible IRA clarification

I created a traditional IRA account for the first time last year and am confused about the finer details of tax treatment and filing my returns this year. 

 

This is my scenario:

 

1. Opened Traditional IRA account AFTER I filed my 2020 returns (I did this before the tax deadline in April) : I did this with after-tax dollars. 

2. I added a total of $12,000: $6000 for 2020 (late contribution) and $6000 for 2021. 

3. Did a Roth conversion on the entire $12,000 in 2021. 

4. The 2021 portion of that (contribution + conversion) I think I got figured out....I have a 1099-R and I am simply following the corresponding prompts in Turbotax. 

5. It's the 2020 portion I am a bit confused about. I did NOT submit a Form 8606 in 2021 as part of my 2020 returns. 

 

What should I be doing here? If I submit a standalone 2020 8606 to the IRS right now , is that sufficient? 

 

Would appreciate the advice. 

 

Thanks!