Did you efile? Was it Accepted?  You either entered your bank account for the IRS to pull it out of your bank account or you send in a check.

How to pay a tax due

https://ttlc.intuit.com/community/tax-payments/help/how-can-i-pay-my-federal-taxes/00/26212

You can pay the IRS directly at

https://www.irs.gov/payments

Or here is a 1040V voucher slip

https://www.irs.gov/pub/irs-pdf/f1040v.pdf

VolvoGirl gave you information on how to pay your federal tax. Do you also owe state tax? That has to be paid separately, and it goes to a different place. The details are different for each state.