Hello Beth,
You don't file the 1099-K, you will receive a 1099-k, 1099-misc or 1099-nec from the entity or person giving you the money (Venmo, Cash App, etc).
You would report the income on schedule 1 of your tax return if it is a hobby and no expenses can be taken
If it is a business the you will need to file a schedule C (self employment income). On the schedule C you will list all the income you made cash, 1099-K, 1099-nec or 1099-misc.
You will also list all of your expenses associated with making that income. The expenses will be deducted from the income giving you a net profit/loss
Here are a few links with more information
https://turbotax.intuit.com/tax-tips/self-employment-taxes/beginners-tax-guide-for-the-self-employed...
https://turbotax.intuit.com/tax-tips/small-business-taxes/when-the-irs-classifies-your-business-as-a...
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