In TurboTax (TT), enter at:
Federal Taxes Tab (Personal for H&B version)
Deductions & Credits
-Scroll down to:
--Education
--Education Expenses
Some people are reporting that TT will not let them go back to the beginning to change their original entry (or if they accidentally skipped the tuition entry section).
If that is your case,
Go through the entire education interview until you reach a screen titled "Your Education Expenses Summary". Click edit next to the student's name. That should take you to a screen “Here’s your Education Summary”. Click edit next to the section you want to change; tuition, in your case.