You do not enter a dependent child's earned income from wages reported on a W-2 or income from self-employment on your tax return. The dependent can file their own tax return and indicate on the return that they can be claimed as a dependent on someone else's return.
The dependent child does not have to file a tax return if the wages reported on the W-2 were less than $6,300 but if taxes were withheld they should file a tax return for a refund. If the income was from self-employment of $400 or more then they would be required to file a tax return.
Your state may have different filing requirements than federal for dependents, so check your state tax website for information.
