How (where) do I pay my self employment social security taxes?

[Katiedeleon]

I know how much I owe, but don't know physically where/how to pay them.

[VolvoGirl]

For 2020 taxes?  If you filled out Schedule C for self employment business income and have a net Profit the Schedule SE for self employment taxes is automatically included in your total tax due on 1040 line 23 from Schedule 2 line 4.  

Or do you mean to pay the quarterly estimated payments for 2021?

You send in quarterly estimated payments to cover the self employment tax (FICA). The Self Employment tax (Scheduled SE) is automatically generated if a person has $400 or more of net profit from self-employment. You pay 15.3% SE tax on 92.35% of your Net Profit (If it is greater than $400). The 15.3% self employed SE Tax is to pay both the employer part and employee part of Social Security and Medicare. So you get social security credit for it when you retire.

How to make the Estimated payments
https://ttlc.intuit.com/community/tax-payments/help/how-do-i-make-estimated-tax-payments/00/25875

Here are the blank Estimates and instructions…..
https://www.irs.gov/pub/irs-pdf/f1040es.pdf

[rjs]

The tag below your question indicates that you are using TurboTax Deluxe Online. In TurboTax Deluxe Online you can only enter self-employment income that was reported on a Form 1099-NEC. If you have self-employment income that was not reported on a 1099-NEC you will have to upgrade to TurboTax Self-Employed Online, or use any edition of the CD/Download TurboTax software.