How to claim 3rd Recovery Rebate after filing 2021 tax

I live aboard and didn't know there was a 2021 Economic Impact Payment sent by March 2021. I received a Letter 6475 from IRS in my current foreigner address that I haven't claimed $1400.

 

1. Do I need to amend my 2021 tax to find where to claimed the 3rd Recovery Rebate? On the Amend page, I don't know how to locate to the claim page.

2. Any method to claim it?

 

Thank you!