1099 K

That is self employment income.  To report your self employment income you will fill out schedule C in your personal 1040 tax return and pay SE self employment Tax. You will need to use the Online Self Employed version or any Desktop program but the Desktop Home & Business version will have the most help.

Turbo Tax Beginners Tax Guide for the Self Employed
https://turbotax.intuit.com/tax-tips/self-employment-taxes/beginners-tax-guide-for-the-self-employed/L2HLojrj5

What is form 1099NEC?
https://turbotax.intuit.com/tax-tips/irs-tax-forms/what-is-form-1099-nec/L5fbwIFSn

Here is some IRS reading material……
IRS information on Self Employment
https://www.irs.gov/businesses/small-businesses-self-employed/self-employed-individuals-tax-center

Publication 334, Tax Guide for Small Business
https://www.irs.gov/pub/irs-pdf/p334.pdf

Publication 535 Business Expenses
https://www.irs.gov/pub/irs-pdf/p535.pdf

You pay Self Employment tax on $400 or more of net profit from self-employment in addition to any regular income tax. You pay 15.3% SE tax on 92.35% of your Net Profit 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.