If you have already e-filed or mailed the return, you will need to wait until the IRS has accepted the return. Once they accept it and you have received your refund, then you can amend it. If it gets rejected, you can just make the needed changes and file again.
NOTE: The amend form will be ready for you in mid-February. Once amend form is ready, you can go here and get instruction https://ttlc.intuit.com/questions/1894381 for amending that return
If you have not filed already, see steps here https://ttlc.intuit.com/questions/2594639 for how to enter the 1095-A
See reasons why you'd need to amend below
https://ttlc.intuit.com/replies/3318732
