Where do I enter 529 contributions for Illinois Brightstart? I don't see an option under state filing.

I'm not specifically familiar with your state software. The following is a "generic" answer.

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. 

Here's an older post on how to do it for  IL: https://ttlc.intuit.com/community/college-education/discussion/where-in-turbo-tax-can-i-deduct-illinois-529-plan-contributions-up-to-20k-if-married-filing-jointly/00/2050031

To enter your Section 529 Brightstart contributions in the Illinois portion of TurboTax:

1. Open TurboTax Online
2. Select Tax Home in the left pane
3. On the Hi, let's keep working on your taxes! screen, select the dropdown on the right side of State Taxes, then select Start, Continue or Pick up where you left off
4. Select Prepare State in the left pane
5. Work through the next screens until you reach the Status of your state returns screen
6. Select Start or Continue to the right of Illinois
7. Work through the next screens until you reach the Here's the income that Illinois handles differently screen
8. Select the dropdown to the right of Education: College savings, ABLE accounts, and student loan repayments
9. Select Start to the right of College savings and prepaid tuition plan contributions. 
10. Enter all relevant information in subsequent screens

This is where you'll enter information when you've contributed money to a college savings pool or pre-paid tuition program, including Bright Start and Bright Directions college savings pools, and College Illinois pre-paid tuition programs. 

@harveyburgess