"But how and where shall I report the after tax non-deductible contributions for 2023"
That was reportable on your 2023 tax return on 2023 Form 8606. The 2023 Form 8606 will have $6,500 on line 14 which transfers to line 2 of your 2024 Form 8606.
If your 2023 tax return failed to include the 2023 Form 8606, you'll need to amend.
