You can use the IRS Form 1040-ES and the worksheets to calculate the amount of estimated taxes for 2020. The Form 1040-ES and your payment can be mailed to the IRS. 2020 Q2 is due on or before July 15, 2020
IRS Form 1040-ES - https://www.irs.gov/pub/irs-pdf/f1040es.pdf
Or you can pay 2020 estimated taxes on the IRS payment website using Direct Pay - https://www.irs.gov/payments
