You can enter the income reported on your Form 1099-K as self-employment income on Schedule C, the same as you would report cash, checks, etc.
See this article for more information: IRS Form 1099-K: What Online Business Owners Should Know
What kind of return are you doing? A personal 1040 with Schedule C or a separate Business return like a 1065 or 1120?
In TurboTax Business, enter Form 1099-K under Federal Taxes >> Income >> Service Receipts. There is not a 1099-K income topic for business because your total income should include any amounts reported on a 1099-K.
If you want to tag that income, right-click the entry box and choose "Add Supporting Details." Enter 1099-K on the description line and the amount. This detailed information isn't included on your tax return, but you can track the sources of your income using this feature. You may also see an option to enter your own sales categories with a custom description.