Traditionally the balance due returns are not processed until after 4/15 and it takes the IRS up to 3 months to process and approve the payment plan at which time you will get a letter in the mail. Due to the Covid shutdown those returns will probably not be processed before 7/15 so all you really can do is wait patiently.
If you set up the payments to be auto debited then expect that to happen anytime so don't be caught short in your account. Also check here : https://www.irs.gov/payments/online-payment-agreement-application
