We've already filed our taxes (Individuals) and the money that we owe the Fed is to be withdrawn on April 15. How to we request the 90 day payment deadline extension?

Here is how you can change your payment date.

Thank you so so much!

The IRS also sent me this link and suggested that the withdraw date will be automatically adjusted. Just to be on the safe side though, I'll follow your suggestion. 

https://www.irs.gov/newsroom/payment-deadline-extended-to-july-15-2020