You can only contribute a prorated amount based on the number of months that you were eligible to contribute to an HSA.  Since you were covered by your wife's non-HDHP plan on December 1, 2016, you are not an eligible individual for December, nor can you make a full-year's contribution based on the last-month rule.  In TurboTax, indicate that you were not covered by an HDHP on December 1, 2016, then indicate that other months that you were covered.  TurboTax will inform you of your 2016 HSA contribution limit based on the number of months that you were an eligible individual.