You enter the amount of your EITC on:
-line 8a of form 1040EZ or -line 42a of form 1040A or -line 66a of form 1040 and you file your tax return.
In TurboTax (TT), you just enter your info and it happens automatically. If you don't get the EITC, and think you should, re-enter TT at:
Federal Taxes Tab
Deductions & Credits
-Scroll down to:
-You and your family
--Earned Income Credit