What, if anything, do I do with certificates of credible coverage?

A Certificate of Creditable Coverage (COCC) is a document provided by your previous insurance carrier that proves that your insurance has ended.

You can use it for informational purposes, however, you do not need to enter them into the program. 

Sadly I bought my "marketplace eligible" plan directly from BCBS which says they don't provide a 1095-A. Because I didn't take the credit up front, what do I do in TURBO TAX to flag this to the IRS that I should get the credit?