It depends what type of business entity you started.
If you're a Sole Proprietorship or a Single Member LLC, TurboTax will automatically complete Schedule C for you when you add your self-employment income in TurboTax (usually from Form 1099-NEC or 1099-MISC).
Here's how to add your self-employment income if you didn't receive a 1099-NEC or 1099-MISC:
Open or continue your return
Search for schedule c and select the Jump to link in the search results
Answer Yes to Did you have any self-employment income or expenses?
If you've already entered self-employment work and need to enter more, select Add another line of work
Continue with the on-screen interview until complete
If you need Schedule C to report a 1099-NEC or 1099-MISC, make sure your return is open and search for 1099-NEC or 1099-misc, then select the Jump to link. We'll ask questions about your 1099 income and generate Schedule C if your situations calls for it.