If all of the qualifications for Earned Income Credit are met, TurboTax will automatically include it in your tax return.
One common mistake we've found is that some people inadvertently check the wrong answer to some of the questions during the dependent interview. Please go back to the Personal Info section (tab at the top of the screen) of your tax return and review the information for your child. Make sure you answered all the questions accurately. If your child was born in 2015, he is considered to have lived with you for the whole year. (There's a question about whether your child paid more than half of their own living expenses. Some people inadvertently answer 'Yes', when it should be answered 'No').
Then, you can return to the Earned Income Credit section by going to the Federal Taxes tab > then to Deductions & Credits > Review Earned Income Credit (EIC)