Where do I report the after tax contributions I made to my simple IRA?

I assume that you mean an ordinary IRA, not a SIMPLE IRA, since after-tax contributions to a SIMPLE IRA are not permitted.

Ordinary nondeductible traditional IRA contributions were required to be reported on Form 8606.  After entering a Form 1099-R for a distribution from a traditional IRA, TurboTax will ask if you made any nondeductible contributions.  After answering Yes, TurboTax will ask you to provide the amount from line 14 of the last Form 8606 that you filed.  If you have been using TurboTax all along, the box for this value should already be populated with the correct amount.  Also make sure that you have entered any current-year traditional IRA contribution.  TurboTax will prepare Form 8606 to calculate the taxable and nontaxable amounts of your IRA distributions.

Make sure to click the Continue button on the page that lists the Forms 1099-R that you have entered.