How exactly do I file for 2021 when I have a W2 job but also run my own small business?

[xmasbaby0]

You have self-employment income in addition to your W-2 job, so you will need to use either any version of the desktop software or Self-Employed if you use online TurboTax.   You have to prepare a Schedule C for the self-employment income expenses---which can be done using desktop SW or Self-Employed.   You will pay self-employment tax for Medicare and Social Security as well as ordinary income tax.

Depending on how much you are earning from the business, you  might need to pay estimated quarterly tax.

https://ttlc.intuit.com/questions/1901110-do-i-need-to-make-estimated-tax-payments-to-the-irs

https://ttlc.intuit.com/questions/2903027-how-do-i-report-income-from-self-employment

https://ttlc.intuit.com/community/self-employed/help/what-is-the-self-employment-tax/00/25922

https://ttlc.intuit.com/questions/2902389-why-am-i-paying-self-employment-tax

https://ttlc.intuit.com/questions/1901340-where-do-i-enter-schedule-c

https://ttlc.intuit.com/questions/3398950-what-self-employed-expenses-can-i-deduct

Edited---Oh----and ALL of your 2021 income goes on the same tax return---the W-2 income and the self-employment income.

[xmasbaby0]

@elackey1964 The reply above assumes by "my own small business" you mean a sole-proprietorship, or that you are doing work as an independent contractor.   If you have organized that business as a S-corps, C-corps or multi-member LLC, the answer is quite different.   Post back if that is the case.

[Hal_Al]

You file a regular form 1040.  Your additional forms will now include Schedule C, on which you will report your small business income and expenses.  The net profit (or loss)  will then go on line 3 of Schedule 1, where it will be combined with any additional income and/or adjustments before going on line 8 of form 1040.