How to tell TT we need form-8606 ??

Here is information from TurboTax about Form 8606. 

To trigger the 8606 in TurboTax

For the 4 situations listed at the top of this article, you can trigger Form 8606 with these instructions:

1. Open your return if it isn't already open.
2. Inside TurboTax, search for this exact phrase: IRA contribution information
3. Select the Jump to link in the search results.
4. Proceed through the IRA section, answering questions as you go.
5. When you reach the screen Any nondeductible contributions to your IRA? answer Yes, then continue. We'll generate and fill out the 8606 behind the scenes.

Tip: On joint returns, 8606-T stands for "taxpayer" (first person listed on the return) and 8606-S denotes "spouse."