How to claim clean vehicle credit? I already filed state & federal tax using turbotax. it didn't ask to fill f8936 form.

The IRS Form 8936 Clean Vehicle Credit for tax year 2023 has not been finalized in TurboTax.

The form is scheduled to be available on 02/22/2024.

If you need to claim the Clean Vehicle Credit on the 2023 tax return, you will have to amend the 2023 tax return that was filed.

The Form 1040-X for amending a 2023 tax return will be available on 02/15/2024

You will have to wait for the IRS to either Accept or Reject your filed federal tax return.
If the return is rejected you can make the necessary changes and e-file again.
If the return is accepted you will have to amend your original tax return. An amended return, Form 1040-X, can only be printed and mailed to the IRS if the original tax return was not e-filed. The IRS will take up to 20 weeks or longer to process an amended tax return.

Before starting to amend the tax return, wait for the tax refund to be received or the taxes due to be paid and processed by the IRS.

See this TurboTax support FAQ for amending a tax return - https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-return/amend-change-correct-return-already-filed/L4VjJ9BA2_US_en_US?uid=ld1n99kr