Where do I go to import a pdf of my marriage license?

There is nowhere in TurboTax to do that. TurboTax does not have a copy of your marriage license.   Why do you think you need to do that?  And why do you think TurboTax has it?

You do not need to submit a copy of your marriage certificate.  The irs will believe you if you say you are married and have your wife’s ss# on the tax return.