I received health insurance through marketplace without even knowing this because I was already insured through my employer

[Shannon B1]

If you had healthcare from the marketplace previously and then got coverage through your employer but did not notify healthcare marketplace to cancel coverage then you may have had duplicate coverage.  You can contact the Healthcare Marketplace to clarify your coverage and reporting requirements here.  They should be able to guide you through what steps to take to correct this issue and what will need to be reported on your tax return.  

If you have to report your Form 1095-A, here is a TurboTax Help Article on how to enter it.