If you report it on Schedule C as self employment income you will pay about 15.3% SE tax on it in addition to any regular income tax on your total income. So you can send in like 20% to the IRS and some to your state.
Here are the Federal 1040ES instructions and blank forms
http://www.irs.gov/pub/irs-pdf/f1040es.pdf
Or pay them directly on the IRS website. Be sure to pick 1040ES payment for 2019
https://www.irs.gov/payments/direct-pay
