If you earned $400 or more you have to report it as a business on Schedule C. Otherwise, you can report it as Hobby income on line 21 of the Form 1040.
That said, if you have a lot of expenses related to that income, you might want to go ahead and report it on the Schedule C (as a business) because your net loss (if you have one) will be netted with other income on your tax return and reduce your taxable income.
