When you are in your NY return, continue to the screen Changes to Federal Income.
In the Education adjustments section, click on the Start/Revisit box next to New York 529 college savings account activity. On the next screen, Enter New York 529 Contributions, enter your 529 contributions and click Continue. Screen shot at https://ttlc.intuit.com/community/state-taxes/discussion/where-is-the-529-contributions-section-for-...
