There is no federal deduction for making a contribution to a 529 plan.
Some states allow a deduction on the state return. If your state is one, it will come up in the state interview; usually in the "Here's how (your state) handles income differently" section. Most states allow a deduction for each beneficiary.
If it's not self explanatory, when you reach that page/screen, post a new question, identifying the state.
