With the Form 1095-C you will not add this form to your return. The 1095-C is a form titled
Employer-Provided Health Insurance Offer and Coverage. The IRS does not need any
details from this form. The form simply verifies that you had health insurance coverage. You
can keep any 1095-C
forms you get from your employer for
your records.
When you filed your tax return, when asked “Did you have health insurance
coverage in 2016”, you should have checked that you had health coverage all year (if applicable). The next question "Were you enrolled in any of these less common plans in 2016" you would answer "No".That is all that is required to report your health care coverage. Here is an FAQ with additional information What is a Form 1095-C.
Now if you don't recall marking the box for coverage then you would need to Amend. After filing your tax return you need to first wait and see if your return is accepted or rejected. If rejected, you can go back and mark the box to report the coverage then re-submit your return.
If accepted, you need to wait until you receive your tax refund and then Amend your tax return using the Amendment Form 1040X.
Here is an FAQ with additional instructions on Amending your 2016 tax return.
https://ttlc.intuit.com/replies/5114064
