First, before you make any changes, start the amend process in TurboTax. Click this link for instructions on how to file an amended return with TurboTax.
Once you've started the amend process and TurboTax has "frozen" your filed amount, you can make your changes. Click the "magnifying glass Search" icon on the top row, enter "earned income credit" in the search window and press return or enter, and then click on the "Jump to earned income credit" link to start the TurboTax section related to the Earned Income Credit.
The qualification for earned income tax credit (EITC) is based on your adjusted gross income (AGI) and earned income, and the number of eligible children. A good tool for understanding eligibility for EITC is the IRS guide at this link.
If you meet the qualifications and aren't receiving the credit in TurboTax, check your entries. Refer to the TurboTax article at this link for the more details on EITC eligibility.