Thank you for the response.
And I did contact the IRS today. I talked to a very nice lady. She said that all you need to do is call them and let them know the unassessed amount that you will owe (in my case from 2021) and they will add it to the existing payment plan over the phone.
An alternative is to wait until the amount is assessed and call then.
There is an $89 fee to process the change.
