where do I enter 529 contributions on NY State tax form

As you go through your New York state return, you should see a screen with the title Changes to Federal Income.  On that page there is a section for Education Adjustments.  Click Start or Update beside New York 529 college savings account activity to report your contributions.

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-nys-tax-filers-i-only-see-1099q-for-eligible-withdrawls/00/3493385