Are you asking about the quarterly estimated payment? Where to mail is on page 5.
Here are the blank estimate forms and instructions for federal. You need to go to your state's website to get theirs.
https://www.irs.gov/pub/irs-pdf/f1040es.pdf
Or you can pay directly on the IRS website https://www.irs.gov/payments
Be sure to pick the right kind of payment and year.....2019 Estimate
